Dielectric etch chamber with expanded process window

ABSTRACT

A capacitively coupled reactor for plasma etch processing of substrates at subatmospheric pressures includes a chamber body defining a processing volume, a lid provided upon the chamber body, the lid being a first electrode, a substrate support provided in the processing volume and comprising a second electrode, a radio frequency source coupled at least to one of the first and second electrodes, a process gas inlet configured to deliver process gas into the processing volume, and an evacuation pump system having pumping capacity of at least 1600 liters/minute. The greater pumping capacity controls residency time of the process gases so as to regulate the degree of dissociation into more reactive species.

BACKGROUND OF THE DISCLOSURE

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a semiconductor waferprocessing apparatus. More specifically, the invention relates to adielectric etch processing chamber having improved thermal andby-product management capabilities, improved control of gaseous speciesresidence time, and an expanded process window including high flow ratesand low operating pressures.

[0003] 2. Background of the Invention

[0004] One challenge facing all forms of semiconductor processing is theindustry wide progression towards decreasing feature sizes resulting inrapidly shrinking critical dimensions. Current design rules have featuresizes of less than about 0.18 microns and feature sizes below about 0.1microns are being developed.

[0005] Another challenge facing semiconductor processing is the trendtowards smaller footprint devices. One approach to achieving a smallerdevice footprint is to build the device structure vertically and in somedevices, fabricating portions of the device in the substrate itself.

[0006] These challenges generate a need for processing applicationscapable of fabricating high aspect ratio structures and structures withcritical dimensions approaching the sub-0.1 micron range.

[0007] In view of these challenges, minimizing particulate contaminationduring the myriad processing sequences used to fabricate an electronicdevice is critical. Chamber components are selected and processes areperformed in reduced atmospheres to assist in reducing and managingparticles that may be present and/or generated in the processingenvironment. Of particular importance is the management of films thatform within the process chamber during wafer processing.

[0008] Films deposited within the processing chamber are majorcontributors to the total particulate concentrations found within theprocess chamber. Films typically form on exposed chamber and process kitcomponents during a wide variety of semiconductor processingapplications.

[0009] During dielectric etch processes, for example, some of thematerial removed from the layer exposed to the etchant is exhausted fromthe processing chamber. However, some etch reaction by-products formdeposits on exposed chamber surfaces and on surfaces of the etchedstructure.

[0010] The deposits on chamber surfaces increase in thickness as theprocess cycles are repeated and additional wafers are processed. As thedeposit thickness increases, so too does the internal stressesassociated with the deposit. Additional stresses are created in thesedeposits due to differences in thermal expansion rates between thedeposit and the chamber surfaces. Conventional etch chambers lackappropriate thermal management techniques to reduce thermally inducedstresses between accumulated deposits and chamber components.Eventually, the stresses can cause the deposits to crack, consequentlyreleasing particles into the chamber environment. These film particlesmay impinge upon the wafer surface, typically creating a defect in thecircuit structure on the wafer.

[0011] Control of deposit formation on the etch structure is also acritical process consideration. In high aspect ratio dielectric etchprocesses, for example, the formation of a thin sidewall layer orpassivation layer is desired to help maintain sidewall profile controlas the depth of the etched feature increases. As feature sizes decrease,however, sidewall profile control becomes increasingly more difficultand possibly unfeasible using conventional plasma etch chambers.Decreasing critical dimensions require increasingly refined control ofan expanded range of etch process chemistry parameters not provided byconventional etch chambers.

[0012] Therefore, there is a need for a dielectric etch processingapparatus with the capability of providing expanded processingcapabilities with improved process parameter control that enablesadvanced feature dielectric etch processes.

SUMMARY OF INVENTION

[0013] The disadvantages associated with the prior art etch chambers andthe challenges posed by advanced dielectric etch processes are overcomeby embodiments of the present invention of a thermally controlled plasmaetch chamber having an expanded process window and improved byproductmanagement capabilities. The inventive procees chamber is generally acapacitively coupled plasma source chamber and, more specifically, acapacitively coupled chamber operating in an RIE mode and MERIE mode.

[0014] An embodiment of an apparatus according to the present inventioncomprises a capacitively coupled reactor for plasma etch processing ofsubstrates at subatmospheric pressures having a chamber body defining aprocessing volume, a lid provided upon the chamber body, the lid being afirst electrode, a substrate support provided in the processing volumeand comprising a second electrode, a radio frequency source coupled atleast to one of the first and second electrodes, a process gas inletconfigured to deliver process gas into the processing volume, and anevacuation pump system having pumping capacity of at least 1600liters/minute. The greater pumping capacity controls residency time ofthe process gases so as to regulate the degree of dissociation into morereactive species, such as free fluorine.

BRIEF DESCRIPTION OF DRAWINGS

[0015] The teachings of the present invention can be readily understoodby considering the following detailed description in conjunction withthe accompanying drawings, in which:

[0016]FIG. 1 is a cross-sectional schematic view of a parallel platesemiconductor wafer processing system;

[0017]FIG. 2 is a cross-sectional schematic view of a semiconductorwafer processing system illustrating an embodiment of an upper and alower liner according to the present invention;

[0018]FIG. 3A is a plan view of a lid assembly having the first liner ofFIG. 2;

[0019]FIG. 3B is a plan view of another lid assembly;

[0020]FIG. 4 is a partially exploded elevation of the lid assembly ofeither FIG. 3A or 3B;

[0021]FIG. 5 is plan view of the second liner of FIG. 2;

[0022]FIG. 6 is a cross-sectional view of the second liner of FIG. 5taken along section line 5-5;

[0023]FIGS. 7a-7 f are various embodiments of a gas inlet;

[0024]FIG. 8 is a plan view of the ceiling interior surfacecorresponding to FIG. 2.

[0025]FIG. 9 is a plan view of an individual mini-gas distribution plateof the invention having angled gas inlets providing a preferred vortexpattern of gas spray.

[0026]FIG. 10 is a cross-sectional cut-away view corresponding to FIG.9.

[0027]FIG. 11 illustrates an alternative spray pattern corresponding toFIG. 4.

[0028]FIG. 12 is an enlarged cut-away cross-sectional view correspondingto FIG. 2.

[0029]FIGS. 13 and 14 are top and sectional views, respectively, of aplate in which has been formed a texture consisting of squareprotrusions.

[0030]FIG. 15 is a sectional view of an alternative to the embodiment ofFIG. 14 in which the sides of the square depressions are formed at anoblique angle.

[0031]FIGS. 16 and 17 are top and sectional views, respectively, of analternative embodiment in which the depressions are hemispherical inshape.

[0032]FIGS. 18 and 19 are perspective and sectional views, respectively,of a texture consisting of a series of circumferential grooves in acylindrical side wall liner.

[0033]FIG. 20 is a perspective view of a cylindrical liner having bothcircumferential and longitudinal grooves.

[0034]FIG. 21 is a plan view of a plasma etching chamber with an exhaustmanifold having an annular, U-shaped magnet system embedded within anannular protrusion according to the invention.

[0035]FIG. 22 is a detail of the magnet system and annular protrusionsin the FIG. 21 chamber.

[0036]FIG. 23 is a perspective view of an annular, U-shaped magnetsystem with magnetic poles facing radially outward.

[0037]FIG. 24 is a perspective view of a magnet system whose magnets andpole pieces are interchanged relative to the embodiment of FIG. 23.

[0038]FIG. 25 is a perspective view of an annular, U-shaped magnetsystem with magnetic poles facing radially inward.

[0039]FIG. 26 is a perspective view of a magnet system whose magnets andpole pieces are interchanged relative to the embodiment of FIG. 25.

[0040]FIG. 27 is a detailed plan view of an exhaust manifold having twoannular magnets respectively embedded within two annular protrusionsaccording to the invention.

[0041]FIG. 28 is a cross-section partial schematic view of analternative embodiment of the present invention in a capacitivelycoupled, magnetically enhanced reactive ion etch (MERIE) processingsystem;

[0042]FIG. 29 is a cross-section partial schematic view of analternative embodiment of the present invention in a parallel plate etchprocessing system;

[0043]FIG. 30 is a cross-section partial schematic view of analternative embodiment of the present invention in a, capacitivelycoupled, magnetically enhanced reactive ion etch (MERIE) processingsystem generated by a rotating magnetic field;

[0044]FIG. 31 is a cross-section partial schematic view of analternative embodiment of the present invention in an etch processingsystem having an RF driven inductive member;

[0045]FIG. 32 is a cross-sectional schematic view of anothersemiconductor wafer processing system having a chamber liner with ashowerhead gas distribution system and an inductive coil;

[0046]FIGS. 33A and 33B are cross-section views of a representativeself-aligned contact feature;

[0047]FIGS. 34A and 34B are cross-section views of a representative highaspect ratio contact feature;

[0048]FIGS. 35A and 35B are cross-section views of a representative viafeature;

[0049]FIGS. 36A and 36B are cross-section views of a representative maskopen feature;

[0050]FIGS. 37A and 37B are cross-section views of a representativespacer feature; and

[0051]FIGS. 38A and 38B are cross-section views of a representative dualdamascene feature.

[0052] To facilitate understanding, identical reference numerals havebeen used, where possible, to designate identical elements that arecommon to the figures.

DETAILED DESCRIPTION OF INVENTION

[0053] I. Exemplary Processing System

[0054]FIG. 1 illustrates an embodiment of the processing apparatusimprovements of the present invention in an exemplary processing chamber100 for processing a substrate 10, such as a semiconductor wafer. Theinvention will be described below initially with reference toembodiments as used in the exemplary processing system 50 of FIG. 1.However, it should be understood that the description of the inventivefeatures applies to the alternative chamber configurations such as theetch chamber configurations 2800 to 3200 described below with referenceto FIGS. 28 to 32. Embodiments of the present invention are particularlyadvantageous in plasma etch chambers configured for oxide and dielectricetch processes.

[0055] An embodiment of the present invention is illustrated inprocessing system 50 of FIG. 1. Processing system 50 comprises aprocessing chamber 100, a gas panel 105, a computer controller 140, aheat exchanger or temperature controlled fluid source 121, an RF source150, a pump 109, an exhaust system 110 and a cooling gas system 107.

[0056] The processing chamber 100 includes a circumferential sidewall106, a bottom wall 108 and a lid assembly 102 that together define achamber volume 110. A substrate support 124 is disposed on bottom wall108 for supporting the substrate 10. Generally, the chamber volume 110is divided into a process volume 112—the upper region of the chamber—anda pumping volume 114—the lower region of the chamber. Chamber liner 104,illustrated as a first liner 134 and a second liner 118, is disposedadjacent to walls 106,108 and lid 102. In an embodiment described ingreater detail below, chamber liner 104 includes a plasma confinementmeans 52 for confining a plasma within process volume 112.

[0057] The processing chamber 100 is provided with a slit valve 139 oraccess port for transferring substrates from a common loadlock ortransfer area into the processing region 112. A robot 53 (shown inphantom in FIG. 1) is used to transfer substrates in and out ofprocessing region 112. A slit valve door (not shown) provides a vacuumseal of the slit valve opening 139. A liner door 70 could be avertically actuated via a pneumatic motor 72 as illustrated in FIG. 1 tocover the opening in the chamber liner 104 adjacent the slit valveopening 139.

[0058] Substrate support 124 may use electrostatic force or mechanicalclamping force to ensure the substrate 10 remains in place duringprocessing. If electrostatic force is used, substrate support 124includes electrostatic chuck 55. A lift pin assembly 155 comprises liftpins 160 a,b that are elevated through holes in the electrostatic chuck55 by a pneumatic lift mechanism 170. The robot 53 places the substrate10 on the lift pins 160 a,b, and the pneumatic lift mechanism 170 lowersthe substrate 10 onto the receiving surface of electrostatic chuck 55.After the substrate 10 is placed on the electrostatic chuck 55 and priorto conducting a process, an electrode 105 embedded in the electrostaticchuck 55 is electrically biased with respect to the substrate 10 toelectrostatically hold the substrate 10.

[0059] On completion of the process, the pneumatic lift mechanism 170raises the lift pins 160 to raise the substrate 10 off the receivingsurface of electrostatic chuck 55, allowing the substrate 10 to beremoved by the robot 53. Before raising the lift pins 160 a,b, thesubstrate 10 is electrically decoupled or de-chucked by dissipating theresidual electrical charges holding the substrate 10 to theelectrostatic chuck 55.

[0060] In the embodiment illustrated in FIG. 1, electrostatic chuck 55is formed from a dielectric that envelops and electrically isolates theelectrode 105 from the substrate 10. Preferably, the dielectric is aceramic material, such as Al₂O₃, AIN, BN, Si, SiO₂, Si₃N₄, TiO₂, ZrO₂,codierite, mullite, or mixtures and compounds thereof. In oneembodiment, the electrostatic chuck 55 is formed from a high thermalconductivity ceramic material with a resistivity selected for optimalperformance in the temperature range that the substrate 10 ismaintained. For example, resistivity in the range of between about 5 e¹⁰Ω-cm to about 5 e¹³ Ω-cm, for example, have been used where substratetemperatures in the range of between about −20° C. to about 50° C. aredesired.

[0061] An electrode 105 disposed within substrate support 124 couples RFenergy into process volume 112. RF energy from RF source 150 is coupledto electrode 105 via impedance matching circuitry 151. Electrode 105 maybe formed from an electrically conducting material, such as a metal, forexample, aluminum, copper, molybdenum or mixtures thereof. Generally,electrode 105 has a robust construction that allows coupling of up toabout 5000 Watts of RF power from RF generator 150. The exact amount ofRF power coupled through robust electrode 105 varies depending upon theparticular etch process conducted within etch chamber 100.

[0062] A backing plate 161 is disposed adjacent to electrostatic chuck55. The backing plate 161 has internal cooling channels supplied withtemperature controlled fluid from heat exchanger 121 via inlet 163. Thetemperature controlled fluid, such as for example, an ethylene glycoland de-ionized water mixture, circulates through the conduits in thecooling plate. Preferably the electrostatic chuck 55 is attached to thebacking plate 161 so as to maximize heat transfer from the electrostaticchuck 55 to the backing plate cooling channels and thence to thetemperature controlled fluid.

[0063] In another aspect of the present invention, the backing plate 161is bonded or joined to the electrostatic chuck 55 by a bond layer madefrom a material having high thermal conductivity. The bond layer cancomprise, for example a metal, such as aluminum, copper, iron,molybdenum, titanium, tungsten or alloys thereof, such as for example,titanium diborite. The bond layer eliminates use of bolts for securingthe electrostatic chuck 55 to the cooling plate 161 and consequentlyreduces mechanical stresses on the electrostatic chuck 55. Also, thebond layer has a homogeneous composition that provides more uniform heattransfer rates across the substrate 10, and reduces the differences inthermal impedances that occur at the interface between the cooling plate161 and the electrostatic chuck 55.

[0064] Preferably, the bond layer is ductile and compliant to provide aninterface that absorbs the thermal stresses arising from the thermalexpansion mismatch between the electrostatic chuck 55 and the coolingplate 161 without damaging the electrostatic chuck 55. While a bondedjoint provides uniform heat transfer rates, it is often difficult for abonded joint to withstand the thermal stresses arising from differencesin thermal expansion coefficients of dissimilar materials, such as theelectrostatic chuck 55 and the cooling plate 161. An exemplary bondlayer is made from a ductile and compliant material that can flex andabsorb thermal stresses that arise from the difference in thermalexpansion coefficients of the electrostatic chuck 55 and the coolingplate 161. One suitable bonding material consists of a high bondstrength, pressure sensitive acrylic adhesive, loaded with titaniumdiboride and applied to an expanded aluminum carrier. The combination offiller, expanded metal and embossed surface enhances the conformabilityand thermal performance of the bond.

[0065] The temperature of the substrate 10 is controlled by stabilizingthe temperature of the electrostatic chuck 55 and providing a coolinggas, such as helium, from cooling gas source 107 to channels formed bythe back of the substrate 10 and grooves formed on the receiving surfaceof electrostatic chuck 55. The cooling gas facilitates heat transferbetween the substrate 10 and the electrostatic chuck 55. The spacebetween the backside of the wafer 10 and the receiving surface of theelectrostatic chuck 55 is preferably divided into two zones—an innerzone and an outer zone. Separate flow controllers 107 ₀ and 107 ₁ areused to provide independent cooling gas flow control to the outer andinner zones, respectively. Typically, the desired amount of cooling gasis measured in pressure, generally, in Torr.

[0066] Separate zone controllers 107 ₁ and 107 ₀ allow the zones to bemaintained at the same pressure or at different pressures. Adjusting thepressure in the inner and outer zones leads to a correspondingadjustment in the temperature at the center and edge of the substrate10. Thus, by adjusting the pressure of the inner and outer zones thetemperature profile across the substrate 10 is controlled. Thetemperature across the substrate 10 may be adjusted to compensate forthe specific temperature requirements of a particular etch process. Forexample, the temperature across the substrate may be uniform from centerto edge, have a higher edge temperature than center temperature or havea higher center temperature than edge temperature.

[0067] During plasma processes, the substrate 10 is heated by plasma inthe chamber and the dual zone cooling gas control is used to adjust thesubstrate temperature. Typically, substrate 10 is maintained in atemperature range of between about −20 to about 150 degrees Celsius witha preferred operating range of about 15 to about 20 degrees Celsius. Theinner and outer cooling gas zones can also be operated to induce athermal gradient across substrate 10. For example, the inner zone andthe outer zone cooling gas pressures can be adjusted so that thetemperature in the center of the substrate 10 is greater than or lessthan the temperature at the edge of the substrate 10. In addition, theinner and outer cooling gas zones may be adjusted so that thetemperature difference across the center to edge of the substrate 10 isabout 5 C. or where the temperature between the center and edge remainsnearly constant.

[0068] The components of substrate support 124 including cooling plate161, an electrostatic chuck 55, dual zone backside cooling gas androbust electrode 105 cooperatively operate to remove heat generatedduring plasma processing operations conducted in chamber 100. Thethermal management and temperature control features enable processingoperations that employ higher RF powers and higher magnetic fields (forchambers using magnetically enhanced processing) for longer processtimes because the temperature of substrate 10 can be efficientlycontrolled even during processes combining both RF power levels above2500W and magnetic fields greater than 100 G. The temperature controland thermal management capabilities of etch chamber 100 are furthered bythe direct temperature control feature of liners 118 and 134 describedbelow in section II entitled “Temperature Controlled Chamber Liner.”

[0069] Gas panel 105 includes process gas supplies and flow controlvalves which under the control of computer controller 140 provideprocess gases to process chamber 100. Process gases from gas panel 105are provided via piping 103 through lid assembly 102 to a plurality ofgas inlets or nozzles 350. A plurality of nozzles 350 are distributedacross the lid assembly 102 for providing process gases into processingvolume 112 as described in greater detail below in section III entitled“Thermally differentiated Gas Supply System”.

[0070] In operation, a semiconductor substrate 10 is placed on thesubstrate support 124 and gaseous components are supplied from the gaspanel 105 to the process chamber 100 through nozzles 350 to form adesired gas composition in the processing volume 112. The gascomposition is ignited into a plasma in the process chamber 100 byapplying RF power from the RF generator 150 to impedance matchingcircuitry 151 to the electrode 105. The plasma formed from the gascomposition is in contact with the temperature controlled surfaces ofthe lid assembly 102 and the liner 104.

[0071] The pressure within the process chamber 100 is controlled using athrottle valve 8 situated between the chamber volume 110 and a vacuumpump 109. In a preferred embodiment, the pump 109 provides a pumpingcapacity of greater than about 1000 liters per second, preferablybetween about 1,400 to 2,000 liters per second, and more preferablyabout 1,600 liter per second. Pump 109 may be a single high capacityvacuum pump or a combination of a vacuum pump and a turbo pump. Underthe control of controller 140, the pump 109 and the throttle valve 8cooperatively operate to provide an advantageously expanded pressure andgas flow rate plasma etch processing regime. In a preferred embodiment,the plasma etch chamber is a thermally controlled etch chamber capableof performing both magnetically enhanced reactive ion etching (MERIE)and reactive ion etching (RIE) etch processes in a low pressure—hightotal gas flow regime, such as for example, a total gas flow of morethan about 350 sccm and a chamber pressure of less than about 80 mT.Preferably, an embodiment of a process chamber according to the presentinvention enables chamber pressures below about 50 mT with total flowrates of about 1000 sccm.

[0072] Plasma etch chambers having embodiments of the present inventionare capable of low pressure—low flow dielectric etch processes such asfor example, spacer etching and mask open etching generally conducted atpressures of between about 10 mT to about 80 mT with total gas flowrates of from about 40 sccm to about 150 sccm. Plasma etch chambershaving embodiments of the present invention are also capable ofhigh-pressure high flow rate dielectric etch processes such as, forexample, C₄F₈ and C₂F₆ based etch processes conducted at pressures ofbetween about 150 mT to about 300 mT and total gas flow rates of betweenabout 350 sccm to about 700 sccm. Plasma etch chambers havingembodiments of the present invention are also capable of high total gasflow—low chamber pressure etch processes such as, for example, C₄F₆ andCH₂F₃ based etching of self aligned and high aspect ratio contacts atpressures of from between about 10 mT to about 120 mT and total gas flowrates of between about 600 sccm to about 900 sccm.

[0073] Additionally, plasma etch chambers having embodiments of thepresent invention enable etch processes in a variety of processingregimes, such as for example, an etch process regime with a total gasflow ranging from about 120 sccm to about 400 sccm at a chamber pressureranging from about 70 mT to about 120 mT; an etch processing regime witha total gas flow ranging from about 100 sccm to about 450 sccm atchamber pressures ranging from about 20 mT to about 70 mT; and an etchprocessing regime having total gas flows ranging from about 300 sccm toabout 800 sccm at chamber pressures ranging from about 20 mT to about 70mT. Section VII below entitled “Chamber Process Window AndRepresentative Critical Dielectric Etch Processes” provides additionaldetails of the improved oxide and dielectric etch process window enabledby plasma etch chambers having embodiments of the present invention.

[0074] A controller 140 comprising a central processing unit (CPU) 144,a memory 142, and support circuits 146 for the CPU 144 is coupled to thevarious components of the process chamber 100 to facilitate control ofthe chamber. To facilitate control of the chamber as described above,the CPU 144 may be one of any form of general purpose computerprocessors that can be used in an industrial setting for controlling thevarious chamber components and even other processors in a processingsystem where computer controlled chamber components are utilized. Thememory 142 is coupled to the CPU 144. The memory 142, or computerreadable medium, may be one or more of readily available memory such asrandom access memory (RAM), read only memory (ROM), floppy disk drive,hard disk, or any other form of digital storage, local or remote. Thesupport circuits 146 are coupled to the CPU 144 for supporting theprocessor in a conventional manner. Support circuits 146 include cache,power supplies, clock circuits, input/output circuitry and subsystems,and the like. A process, such as the etch process, is generally storedin the memory 142, typically as a software routine. The software routinemay also be stored and/or executed by a second CPU (not shown) that isremotely located from the hardware being controlled by the CPU 144.

[0075] The software routine executes a process, such as an etch process,to operate the chamber 100 to perform the steps of the process. Whenexecuted by the CPU 144, the software routine transforms the generalpurpose computer into a specific process computer (controller) 140 thatcontrols the chamber operation to perform the steps of the process.Although embodiments of the present invention are discussed as beingimplemented as a software routine, some or all of the method steps thatare discussed herein may be performed in hardware as well as by thesoftware controller. As such, the invention may be implemented insoftware and executed by a computer system, in hardware as anapplication-specific integrated circuit or other type of hardwareimplementation, or in a combination of software and hardware.

[0076] II. Temperature Controlled Chamber Liner

[0077] Temperature controlled chamber components, such as a chamberliner 104 and lid assembly 102, for use in an etch processing systemsuch as processing system 50 may be better appreciated by reference toFIGS. 2-6. Embodiments of the present invention also provide methods forcontrolling the temperature of chamber components, to substantiallyimprove adhesion of deposits formed on these chamber components.

[0078]FIG. 2 is a cross sectional view of one embodiment of an etchchamber 100 of the present invention having a chamber liner 104. Theetch chamber 100 is configured as a parallel plate etch reactor.Generally, the chamber liner 104 comprises a first (first) liner 134, asecond (second) liner 118, or both a first liner 134 and a second liner118. Disposed within each chamber liner 104 is at least one passageformed at least partially therein having an inlet and outlet adapted toflow a fluid through the passage from a temperature controlled, fluidsupply system, such as heat exchanger 121. To facilitate description ofthe liner of the present invention, an embodiment of the liner of thepresent invention will be described as having a first 134 and a second118 liner. One of ordinary skill will appreciate that a single piece,removable liner may be fabricated and used in lieu of upper 134 andlower 118 liners. It is also to be appreciated that different sizedupper 134 and lower 118 liners may be utilized and that the embodimentsillustrated herein are used merely as an aid in describing the presentinvention. The upper liner 134 and lower liner 118 will now be discussedin turn.

[0079] The chamber 100 generally includes an annular sidewall 106, abottom wall 108, and a lid assembly 102 that define a chamber volume110. Generally, the chamber volume 110 is bifurcated into a processvolume 112 (the upper region of the chamber) and a pumping volume 114(the lower region of the chamber).

[0080] The bottom wall 108 has a pumping port 138 through which excessprocess gases and volatile compounds produced during processing areexhausted from the chamber 100 to exhaust system 110 by a vacuum pump109. The bottom wall 108 additionally has two apertures 116 (only one ofwhich is shown in FIG. 2) that provide access to the second liner 118from the exterior of the chamber 100.

[0081] Embodiments of the lid assembly 102 are detailed in the planviews of FIGS. 3A, 3B and cross-sectional view of FIG. 4. In oneembodiment illustrated in FIG. 4, the lid assembly 102 comprises thefirst liner 134 and a lid 202. The first liner 134 has an outwardlyextending flange 342 that rests upon the top of the sidewall 106. Thevarious components of lid assembly 102 are appropriately configured toprovide a gas tight seal where needed to ensure the vacuum integrity ofthe processing volume 112. For example, lid assembly 102 may begenerally biased downwardly when the lid 202 is clamped in place, thelid assembly 102 exerts a downward force upon the second liner 118 wheninstalled in the processing chamber 100.

[0082] Continuing with FIG. 4, the first liner 134 is fabricated from athermally conductive material, such as for example, anodized aluminum,stainless steel, ceramic or other compatible material. The first liner134 can be easily removed for cleaning and provides a removable surfaceon which deposition can occur during processing. The first liner 134comprises a center section 310 having a dish-shaped top surface 312, anda bottom surface 316. The dish-shaped top surface 312 has a perimeter314 that is connected to the outwardly extending flange 342. Extendingfrom the bottom surface 316 is a cylindrical liner wall 318. The bottomsurface 316 and liner wall 318 have interior surfaces 320 that areexposed to the process volume 112. As described in greater detail belowin section IV, the interior surfaces 320 of upper liner 134, oroptionally, any liner exposed to process volume 112 may be textured toimprove adhesion of deposited films by reducing surface tension in thefilm.

[0083] A fluid passage 322 is disposed within center section 310. Thefluid passage 322 may be formed by a number of conventional means suchas, for example, forming the fluid passage 322 during casting. Turningbriefly to FIG. 3A, another method for forming fluid passage 322 is bydrilling a number of intersecting blind holes 208 wherein each hole 208is sealed by a plug 210, thus forming the fluid passage 322.

[0084] Returning to FIG. 4, two bosses 326 (only one of which is shownin FIG. 4) protrude from the surface 312 of the center section 310. Eachboss 326 has a center hole 328 that is fluidly coupled to the fluidpassage 322 via the respective bore 324.

[0085] The fluid passage 322 receives fluid from the heat exchanger orcoolant source 121. Like all surfaces exposed to the plasma, first liner134 is heated by plasma processes conducted in the plasma etch chamber.The fluid regulates the temperature of the first liner 134 by drawingheat conducted through the first liner 134 into the fluid. As the fluidis circulated through the first liner 134 from the fluid source 121, theamount of heat removed form the first liner 134 is controlled, thuspermitting the first liner 134 to be maintained at a predeterminedtemperature.

[0086] The fluid, which may be liquid and/or gaseous fluids, is flowedthrough the fluid passage 322 to provide temperature control to thefirst liner 134. The fluid is preferably a liquid such as de-ionizedwater and/or ethylene glycol. Other fluids, such as liquid or gaseousnitrogen or freon, can also be used. Alternatively, the first liner 134could be uniformly heated using heated fluids.

[0087] One skilled in the art will be able to devise alternateconfigurations for the fluid passage utilizing the teachings disclosedherein. For example, as depicted in FIG. 3B, a lid assembly.202 maycomprise a first fluid passage 322A and a second fluid passage 322B. Thefirst and second fluid passages 322 A and B may share a common inlet330i and a common outlet 330o as illustrated in FIG. 3B. Optionally,additional inlets and outlets may be utilized. The first and secondfluid passages 322 A and 322 B double back in a “two tube pass”configuration. Additional tube passes may alternatively be incorporated.

[0088] Returning to FIGS. 3A and 4, quick-connect fluid couplings areutilized to fluidly connect a fluid supply 121 and the first liner 134to facilitate the rapid removal and replacement of the first liner 134from the chamber 100. Typically, a quick-connect 330 having a male pipethread-form is threaded into a female thread-form in the center hole 328of the boss 326. The mating coupling 332 is affixed to the terminal endof a fluid supply line 334. The fluid supply line 334 couples thepassage 322 to the fluid supply 121. One advantage of this configurationis that during the change out of the first liner 134, the fluid supplyline 334 can be disconnected without the aid of tools. However, othermeans of coupling the first liner 134 to the fluid supply line 334 (forexample, pipe threads, barbed nipples, collet connectors and the like)may also be used. Quick-connects are commercially available and aregenerally selected based on port size (thread-form and flow capacity)and the brand used in a particular wafer processing facility or fab (formaintenance inventory purposes).

[0089] Returning to FIG. 4, the liner wall 318 is sized to slip insidethe sidewall 106 with minimal clearance. The liner wall 318 may vary inheight, and may, when used without a second liner, extend to the chamberbottom 108. Generally, if both the first liner 134 and second liner 118are utilized (as shown in FIG. 2), the liners are proportioned to fitinside the chamber 100 to provide the compressive force necessary toseal the second liner 118 to the chamber bottom 108 when the lidassembly 102 is clamped in place.

[0090] The liner wall 318 may additionally contain a number of otherports for various purposes. An example of such other ports is asubstrate access port to align with the slit opening of the chamber 100.

[0091] Returning to FIG. 2, the second liner 118 will now be described.The second liner 118 is disposed in the chamber 100 to surround thesubstrate support 124 and form a deposition area that can be easilyremoved and cleaned.

[0092] The second liner 118 has a fluid passage 119 in which fluid isprovided from the fluid source 121 by a conduit 123. As with theoperation of the first liner 134, the fluid regulates the temperature ofthe second liner 118 by drawing heat conducted through the second liner118 into the fluid. As the fluid is circulated through the second liner118 from the fluid source 121, the amount of heat removed form thesecond liner 118 is controlled, thus permitting the second liner 118 tobe maintained at a predetermined temperature.

[0093]FIGS. 5 and 6 depict the second liner 118 in greater detail. Thesecond liner 118 is fabricated from a thermally conductive material, forexample anodized aluminum, stainless steel, or other compatiblematerial. The second liner 118 comprises a base section 502 connectingan inner wall 504 and an outer wall 506. The interior surfaces 508 ofthe base section 502, inner wall 504 and outer wall 506 are exposed tothe pumping volume 114. As described in greater detail below in sectionIV entitled “Chamber Surface Alterations to Improve Adhesion,” and withregard to the alternative embodiments illustrated in FIG. 8 and FIGS.13-20, the interior surfaces 508 may be textured to increase improveadhesion of deposited films by reducing surface tension in the film.

[0094] The base section 502 contains a fluid passage 119. The fluidpassage 119 may be formed by conventional means such as those describedabove with regard to the first liner 134. In one embodiment, the fluidpassage 119 is substantially circular, beginning and ending adjacent toan exhaust port 520 that is disposed through the second liner 118.

[0095] Each end of the fluid passage 119 terminates in a boss 510 thatprotrudes from an exterior surface of the base 502. The boss 510interfaces with the bottom wall 108 and ensures the proper orientationof the second liner 118 in the chamber 100 (i.e., all ports align). Tofacilitate the rapid change out of the second liner 118, quick-connectfluid couplings are utilized between the second liner 118 and a conduit123 that fluidly couples the passage 119 to the fluid source 121.

[0096] The inner wall 504 is generally cylindrical and is sized to slipover the substrate support 124 with minimal clearance. The inner wall504 optionally comprises a plasma containment means 516. Plasmaconfinement means 516 may be, for example, a containment magnet 516disposed within a protrusion 518 formed within inner wall 504 and facingthe outer wall 506. The protrusion 518 is positioned away from the baseon the inner wall 504 so that the plasma containment magnet 516 residesbelow the substrate support 124 when the second liner 118 is installed.The plasma containment magnet 516 may be a samarium magnet 516.Alternative embodiments of the plamsa confinement feature of the presentinvention are described in greater detail below in a section entitledPlasma Confinement. (FIGS. 21 to 27.)

[0097] The outer wall 506 is generally cylindrical and is sized todefine a minimal gap with the chamber walls 106. The outer wall 506 mayvary in height, particularly if a first liner 134 is also utilized asdescribed above. The outer wall 506 additionally contains the exhaustport 520 that aligns with the pumping port 138. The exhaust port 520 maypartially encompass a portion of the base wall 108. The exhaust port 520provides fluid access of gases in the pumping volume 114 to the throttlevalve 8 and vacuum pump 109.

[0098] The outer wall 506 may optionally include a throttling ridge 522extending into the pumping volume 114. The throttling ridge 522 ispositioned proximate the protrusion 518 on the inner wall 504 to createan annular flow orifice 524 for controlling the flow of gases movingfrom the process volume 112 to the pumping volume 114. The outer wall506 may additionally contain a number of other ports for variouspurposes. An example of such other ports is a substrate access port 526that aligns with a slit opening 139 in the sidewall 106 to allowtransfer of substrate 10 in and out of the chamber 100. Turning brieflyto FIG. 28 which illustrates another embodiment of liner 118, outer wall506 does not include a throttling ridge 522 and only protrusion 518extends into pumping volume 114.

[0099] The operation of a temperature controlled liner according to thepresent invention can be illustrated while viewing FIG. 2. In operation,the temperature of the first liner 134 and second liner 118 arecontrolled by flowing fluid through the passages 119 and 322 within therespective liners 118 and 134, from the fluid source 121. The fluidregulates the temperature of the liners 118 and 134 by transferring heatbetween the liners 118 and 134 and the fluid. The fluid from the fluidsource 121 is controlled in both temperature and rate of flow, thuscontrolling the amount of heat removed from the liners 118 and 134, andpermitting the liners 118 and 134 to be maintained at a predeterminedtemperature. In an exemplary embodiment, a user provides a set point forliner wall temperature, for example, into controller 140 and controller140 regulates the amount and temperature of fluid output by heatexchanger 121 to maintain the user input setpoint.

[0100] Because the temperature of the liners 118 and 134 is controlledpredominantly by the fluid in the passages 119 and 322 and less reliantupon conduction with the chamber walls 106, the liners 118 and 134 areable to maintain a substantially uniform, controllable temperatureduring a variety of plasma etch process conditions, such as for example,increased RF powers and higher magnetic fields. Thus, by controlling thetemperature of the chamber liner 104, the amount of material depositedupon the chamber liner 104 can be better controlled and the stresseswithin the deposited material can be minimized thereby improvingadhesion of the deposited material. Because the temperature controlledliners enables improved adhesion of generated by-products, a widervariety of process gas compositions including deposit formingchemistries such as those encountered in oxide an dielectric etchprocess may be used with greater confidence. Process engineers havegreater latitude in devising etch gas compositions because thebyproducts formed by these gas compositions pose less of a contaminationthreat because of the improved adhesion capability of the liners of thepresent invention. In this way, the process window of etch chambershaving embodiments of the present invention are expanded to include awider variety of useable etch gas compositions.

[0101] III. Thermally Differentiated Gas Supply System

[0102] Returning to FIG. 4, an embodiment of the gas distribution systemof the present invention will now be described. The top surface 312 ofthe first liner 134 comprises a center depression 336. The centerdepression 336 is covered by the lid 202, defining a plenum 338 at leastpartially between the lid 202 and the center depression 336. The lid 202additionally has a central hole 340 that allows fluid flow from apassage 344 in a gas feedthrough 212 fastened to the lid 202. The gasfeedthrough 212 is sealed to the lid 202 to prevent gas leakage. The gasfeedthrough 212 is generally coupled to fluid passages within thesidewall 106 as to allow temperature conditioning of gases beingdelivered to the plenum 338 from the gas source (not shown).Alternatively, the gas feedthrough 212 may be directly coupled to thegas source.

[0103] In one embodiment, the plurality of apertures 348 is disposed atleast partially in the center depression 336. The apertures 348 aregenerally positioned in a polar array about the center of the firstliner 134, although other positional locations may be utilized. Eachaperture 348 is fitted with a nozzle 350 a. The nozzles 350 a facilitatedistribution of process and other gases from within the plenum 338 tothe process volume 112 of the chamber 100. The nozzle 350 a is generallyfabricated from a non-conductive material, such as quartz, siliconcarbide, silicon, aluminum nitride, aluminum oxide, Y2O3, Boron Carbide,or other materials such as sapphire.

[0104]FIGS. 7a-7 f depict various alternative embodiments of the nozzle350 a that advantageously minimize recirculative gas flows within thechamber. While reference numbers 350 and 350 a are used, it is to beappreciated that alternative nozzles 350 b to 350 f may be used. Turningnow to FIG. 7A. In one embodiment of the nozzle illustrated in FIG. 7A,the nozzle 350 a includes a mounting portion 717 and a gas deliveryportion 715 that is in communication with the chamber volume 110. Themounting portion 717 has a flange 710 extending from the perimeter ofthe nozzle 350 a typically towards the side of the nozzle 350 a exposedto the plenum 338. The nozzle 350 a additionally comprises a centralpassage 724 that fluidly couples the plenum 338 to the chamber volume110. The central passage 724 generally is positioned co-axially to thecenterline of the nozzle 350 a. Optionally, additional passages may beutilized to fluidly couple the plenum 338 and the chamber volume 110.Additionally, the gas delivery portion of a nozzle may be flush with thefirst liner 134 as illustrated, for example, in nozzle 350 a of FIG. 7Aand nozzle 350 b of FIG. 7B. Alternatively, the gas delivery portion ofa nozzle may extend beyond the first liner 134 as illustrated, forexample, in nozzle 350 c of FIG. 7C, in nozzle 350 d of FIG. 7D, innozzle 350 e of FIG. 7E, and in nozzle 350 f of FIG. 7F.

[0105] Returning to FIG. 7A, the flange 710 mates with a recess 712disposed in the first liner 134. Generally, a contact surface 702 of theflange 710 and a mating surface 704 of the recess 712 have a surfacefinish having a flatness of about 1 mil or less which provides minimalgas leakage between the contact surface 702 and the mating surface 704.A exposed surface 716 of the gas delivery portion 715 may have a smoothor textured surface.

[0106]FIG. 7B illustrates another embodiment of a nozzle, a nozzle 350b, that is substantially similar to nozzle 350 a with the exception thatcentral passage 724 is optional. The nozzle 350 b has a one or morepassages 714 that provide fluid communication of the plenum 338 with thechamber volume 110. Generally, the passages 714 are at an angle to thecenterline of the nozzle 350 b. Optionally, the mounting portion 717 mayextend into the plenum 338.

[0107]FIG. 7C illustrates another embodiment of a nozzle, a nozzle 350c, that comprises the mounting portion 717 and the gas delivery portion735. The gas delivery portion has an end 728 proximate the mountingportion 717 and an opposing, distal end 718 that protrudes into thechamber volume 110. The proximate end 728 is generally coplanar ortangent to a surface of the first liner 134 exposed to the chambervolume 110. The gas delivery portion 735 may have a smooth or texturedsurface finish. A central passage 720 extend at least partially throughthe nozzle 350 c from a side 722 of the mounting portion 717 exposed tothe plenum 338. One or more secondary passages 726 fluidly couple thecentral feed 720 and the chamber volume 110.

[0108] Generally, an outlet 727 of each of the secondary passages 726 onthe exterior of the gas delivery portion 735 are positioned at least adistance “DIST” from the end 728 of the gas delivery portion 735.Additionally, the secondary passages 726 are orientated at an angle θrelative to the proximate end 728. In one embodiment, DIST is greaterthan about 0.25 inches and θ ranges between about 15 and about 35degrees.

[0109]FIG. 7D illustrates another embodiment of the nozzle, nozzle 350d, that is similar to the nozzle 350 c. The nozzle 350 d, however,additionally comprises a central passage 724 that extends along thecenterline of the nozzle 350 c, communicating the plenum 338 directlywith the chamber volume 110.

[0110]FIG. 7E illustrates another embodiment of a nozzle, a nozzle 350e, that is similar to the nozzle 350 d. The nozzle 350 e, however, onlyprovides the central passage 724 between the plenum 338 and the chambervolume 110.

[0111]FIG. 7F illustrates another embodiment of the nozzle, a nozzle 350f, that is similar to the nozzle 350 c. The nozzle 350 f, however, has amounting portion 717 and a gas delivery portion 732 that is at anoblique orientation to the mounting portion 717. The nozzles 350 a-350 fhave been found to run cleaner (i.e., with reduced processing byproductbuildup) than conventional nozzles due to the proximity to the plasmathereby making the nozzles hotter and discouraging deposition ofreaction by-products. Because the gas delivery configuration of thenozzles minimizes flow recirculation within the chamber, the amount ofreaction by-products drawn towards the upper regions (i.e., the lidarea) of the chamber are reduced.

[0112] Common to the nozzles described above is that they have lowthermal mass and are not provided with cooling mechanism. Consequently,they heat up during processing to a temperature above that of the cooledlid and liners, so as to thermally differentiate the nozzles from thelid and liners.. This helps to dramatically reduce polymer deposition onthe nozzles. Optionally, in order to ensure that any polymer that doesget deposited on the nozzles, they are provided with surface roughnessby bid blasting or by a chemical process.

[0113] Additional alternative embodiments of the gas distribution systemare illustrated in FIGS. 8-13. In FIGS. 8-13, in lieu of nozzles 350,mini-gas distribution plates 220 having plural gas injection holes 225are provided in center section 310 of liner 134 to fluidly couple plenum338 and the chamber volume 110. Like nozzles 350, the area of each ofthe mini-gas distribution plates 220 facing the plasma is limited sothat: (1) the area is contained within a region in which the turbulencefrom the injected gas in the vicinity of the inlets prevents or impedespolymer accumulation, and (2) the size or thermal mass of the mini-gasdistribution plate is sufficiently low to allow rapid plasma-heating ofthe plate. In order to enhance the gas turbulence across the area of themini-gas distribution plate 220, the gas injection holes 225 in eachmini-gas distribution plate 220 are angled relative to the surface ofthe plate facing the chamber interior. Preferably, the gas injectionholes are angled so that the gas injection streams from adjacent holescross one another or together form a vortex pattern. In an alternativeembodiment of the placement of the mini-gas distribution plates 220, themini-gas distribution plates 220 extend slightly out from top linersurface 316 to enhance plasma-heating thereof and to enhance gasinjection turbulence. Preferably, the mini-gas distribution plates 220are each a relatively small fraction of the area of the entire ceiling316.

[0114] Each mini-gas distribution plate 220 is formed of a semi-metalsuch as silicon or a dielectric such as silicon dioxide (quartz) orsapphire, or, alternatively, of a non-conductive material or of amaterial compatible with processes conducted within processing chamber100. Each mini-gas distribution plate 220 has plural gas inlets 225through which process gas is sprayed into the reactor chamber interior.Preferably, the mini-gas distribution plates 220 are thermally insulatedfrom the temperature controlled liner 134, so that they are readilyheated by the plasma within the chamber. Each gas distribution plate 220is sufficiently small relative to the ceiling—has a sufficiently smallthermal mass—so as to be rapidly heated by the plasma upon plasmaignition. (For example, the first liner 134 may have a diameter in arange of 9 inches to 14 inches, while a gas distribution plate 220 hasan exposed diameter on the order of about 0.25-0.5 inch. As a result,the plasma heats each mini-gas distribution plate 220 to a sufficientlyhigh temperature to prevent any accumulation of polymer thereon. Theadvantage is that the gas inlets 225 of each mini-gas distribution plate220, like the inlets of nozzles 350, can be kept clear of polymer.

[0115] Preferably, the diameter of each mini-gas distribution plate 220is sufficiently small so that the entire bottom surface 220 a of the gasdistribution plate 220 is enveloped within a region of gas flowturbulence of the process gas spray from the inlets 225. Thus, forexample, each mini-gas distribution plate 220 has an exposed diameter onthe order of about 0.25-0.5 inch. This region has sufficient gasturbulence to retard or prevent the accumulation of polymer on thesurface 220 a.

[0116] Referring to FIGS. 9 and 10, the gas turbulence around the bottomsurface 220 a is enhanced by introducing a crossing pattern of gas spraypaths from the plural gas inlets 225 of the mini-gas distribution plate220. The embodiment of FIGS. 9 and 10 provides a vortex pattern(indicated by the arrows of FIG. 9). This is accomplished by drillingeach of the gas inlets 225 at an angle A (as illustrated in FIG. 10)relative to the outlet surface 220 a of the mini-gas distribution plate220. Preferably, the angle A is in the range of about 20 degrees to 30degrees. In an alternative embodiment illustrated in FIG. 11, the gasspray paths of the plural gas inlets 225 are directed at other inlets inorder to enhance the gas turbulence. This alternative spray pattern isillustrated by the arrows in FIG. 11.

[0117] As a further aid in inhibiting the accumulation of polymer on themini-gas distribution plates 220, the outlet surface 220 a of the plate220 extends slightly below the surface of the ceiling 210 by a distanced, as shown in FIG. 12. The distance d is preferably about 0.02 inch to0.03 inch or a fraction of the thickness of the gas distribution plate220. The enlarged cross-sectional view of FIG. 12 illustrates oneexemplary implementation in which the gas inlets 225 are angled holespassing entirely through the mini-gas distribution plate 220. Processgas is supplied to the gas inlets 225 by a common manifold 230 formed inthe ceiling 316. A water jacket 240 of the water-cooled ceiling 316 isalso shown in the drawing of FIG. 12. Preferably, a thermal insulationlayer 250, which may be aluminum nitride for example, is trapped betweenthe mini-gas distribution plate 220 and the ceiling 316.

[0118] In an embodiment where controlled polymer accumulation is desiredsuch as an oxide etch process for example, the first liner 134 ismaintained at a sufficiently low temperature so that polymer accumulateson the exposed surfaces of the first liner 134 as a very hard film whichis virtually immune from flaking or contributing contamination to thechamber interior. The thermally differentiated mini-gas distributionplates 220 and nozzles 350 are heated by the plasma to a sufficientlyhigh temperature to inhibit accumulation of polymer thereon. Thus, thegas inlets 225 are kept clear of any polymer. The small size of themini-gas distribution plates 220 and nozzles 350 enables the plasma toefficiently heat them to a temperature above a polymer depositiontemeprature. The small size also permits the concentration of gas inletsover the small surface 220 a to provide sufficient gas turbulence tofurther inhibit the accumulation of polymer on the surface 220 a, inlets225, or nozzles 350. The gas turbulence is enhanced by providing acrossed or vortex pattern of gas spray paths from each of the gas inlets225 of the mini-gas distribution plate 220, and having the outletsurface 220 a below the ceiling 316.

[0119] Another advantage of the minimized size nozzle is that becausethe nozzles size is small relative to the temperature controlled lid,plasma formed in the processing volume will likely contact thetemperature controlled lid surface thereby improving byproduct adhesionto the lid as described above. The combination of all of the foregoingfeatures prevents any observable accumulation of polymer on any portionthe mini-gas distribution plate 220 or the various nozzle embodiments.

[0120]FIG. 8 illustrates an embodiment where there are four mini-gasdistribution plates 220 mounted on the first liner 134 at foursymmetrically spaced locations overlying the periphery of the wafer 10.FIG. 8 also illustrates a plurality of semi-spherical bumps formed onthe surface of the ceiling. These bumps are about 0.5 to about 1.5 mmhigh and are spaced about 1 mm apart. Bumps 300 are yet anotheralternative embodiment of the chamber surface texturing described inmore detail below in the next section entitled “Chamber SurfaceAlterations to Improve Adhesion”. Of course, additional mini-gasdistribution plates 220 or nozzles 350 may be provided in otherembodiments, or their placement modified from the arrangementillustrated in FIG. 4 and 8.

[0121] IV. Chamber Surface Alterations to Improve Adhesion

[0122] Another advantage of the present invention is the use of chambersurface topography to improve the adhesion of by products deposited onchamber surfaces. For example, in a conventional fluorocarbon basedplasma etch of oxide features, polymeric byproduct formation is common.Referring to FIG. 2, for example, by-product deposition would occur onthe surfaces of the two liners 118, 134 and lid 102 exposed to theplasma 148. After the deposits accumulate to a certain thickness, thedeposits will begin to flake off the lid and the chamber liners, therebycontaminating the semiconductor devices being fabricated.

[0123] It is believed this aspect of the present invention furtherimproves adhesion of reaction byproducts or other material deposited onsurfaces within the process chamber that are exposed to process gases,thereby allowing the chamber to be operated for longer time intervalsbetween cleaning such surfaces. Moreover, the improved byproductadhesion capability promotes the use of expanded process gascompositions-including those with high rates of byproduct formation.Specifically, chamber interior surfaces such as the surface of thetemperature controlled liner and lid, are fabricated with a surfacecontour or “texture” having topographical features—i.e., alternatingprotrusions and depressions (peaks and troughs)—whose width, spacing,and height dimensions are between 100 microns (0.1 mm) and 100 mm, andpreferably in the range of 500 microns (0.5 mm) to 8000 microns (8 mm).In contrast, the average roughness of surfaces treated by conventionalbead blasting is about 4 to 6 microns (0.15 to 0.23 mil), which is atleast 16 times smaller than the features of the invention.

[0124] By “topographical feature” or “elevation feature” of the surfacewe mean an area whose elevation deviates from the average surfaceelevation. A topographical feature can be either a convex protrusion ora concave depression. The “height” of a feature is the peak-to-troughdeviation in elevation. If the feature is a concave depression, the“height” of the feature is the depth of the depression.

[0125] It is believed that our textured surface improves adhesion of thedeposited material for at least two reasons. One reason is that verticalcontours (contours perpendicular to the average surface plane) increasecompressive forces within the deposited film in a direction normal tothe surface, thereby resisting cracking of the film due to thermalexpansion and contraction. A second reason is that a textured surfacehas a greater surface area for the material to bond to than a flatsurface.

[0126] The surface area increases in proportion to the depth of thedepressions or the height of the protrusions. While increasing theheight dimension in order to increase the surface area by improvesadhesion of deposited material, increasing the height beyond a certainvalue can become disadvantageous. First, an excessive height dimensioncan make the textured surface harder to clean. Secondly, if the texturedsurface is a thin, removable chamber lid or liner rather than acomparatively thick chamber wall, an excessive height dimension canreduce the strength and rigidity of the lid or liner, making it moresusceptible to accidental damage.

[0127] The texturing of our invention can be applied to the surface ofany component of the process chamber. (By “component” we mean any objectin or on the chamber.) The texturing preferably should be applied to anylarge surface that is exposed to the process gases in the chamberinterior and that is either above or near the wafer. The chambersurfaces for which it is most important to provide the texture of theinvention typically are the lower surface of the chamber roof (i.e.,interior surfaces of the chamber lid 102) and the liners 134 and 118.Since the chamber roof is directly above the wafer being processed, anyparticles that flake off of the roof probably will fall on the wafer,thereby causing a defect in the wafer. Since the chamber side wall orlining is very close to the perimeter of the wafer, there also is a highrisk that particles flaking off the side wall or lining will fall on thewafer. It is much less important to provide textured surfaces on chambercomponents positioned below the wafer, since particles flaking off ofsuch surfaces are unlikely to deposit on the wafer.

[0128] Different shapes and dimensions of depressions and protrusions inthe exposed surfaces of the chamber roof and side wall lining weretested. All shapes tested greatly improved adhesion of depositedmaterial compared with either smooth, untreated surfaces or surfacesroughened by bead blasting.

[0129] Viewed in conjunction with FIG. 4, FIGS. 13 and 14 are top andsectional views, respectively, of a portion of the lower surface 316 ofa liner 134 having a texture 60 consisting of a 2-dimensional array ofsquare protrusions 60. For clarity, apertures 348 and nozzles 350 havebeen omitted. The protrusions have height H, width W, and spacing Sbetween adjacent protrusions. FIG. 15 shows a texture 60 a in which thetopographical features are square depressions into the surface ratherthan protrusions, and in which the sides of the square depressions areformed at an oblique angle θ relative to the horizontal surface betweenthe depressions, so that each depression is shaped as an inverted4-sided pyramid with a flat bottom rather than a sharp apex. FIGS. 16and 17 are top and sectional views of an alternative texture 1605 inwhich the depressions are rounded or hemispherical in shape.

[0130]FIGS. 18 and 19 are perspective and sectional views, respectively,of a texture consisting of a plurality of circumferential grooves 1805in a liner 118.

[0131]FIG. 20 is a perspective view of a liner 118 having bothcircumferential 1805 and longitudinal 1810 grooves.

[0132] While each topographical feature has been characterized as eithera protrusion or a depression, it is equivalent to consider the areabetween the depressions to be protrusions on the surface. In otherwords, it is arbitrary whether the protrusions or the depressions aredesignated as the topographical features. Therefore, referring forexample to FIG. 17, the spacing S between depressions or protrusionspreferably should be the same order of magnitude as the width W. Morepreferably, the spacing S and width W should differ by a factor of 2 orless. Similarly, the height H preferably should be the same order ofmagnitude as the width W and spacing S, and more preferably should bewithin a factor of 2 of those other two dimensions.

[0133] In any of the embodiments, we expect the adhesion of thedeposited film to the textured surface will maximized if there are nosharp corners in the textured surfaces of the chamber components,because sharp corners generally increase stress in the film.Consequently, the edges of the topographical features should haverounded corners, with as high a radius of curvature as practical.Preferably, the radius of curvature ranges from between 130 microns(0.13 mm) to about 500 microns (0.5 mm).

[0134] Test Results—Control

[0135] We tested the invention by using a plasma etch chamber to performa plasma process for etching films of silicon dioxide on silicon wafers,using a conventional fluorocarbon etchant gas mixture including C₄F₈ andCO. For the control, the process chamber had an aluminum nitride ceramicroof and an anodized aluminum side wall liner, both of which were smooth(i.e., had no surface texture treatments to improve adhesion.) Theetching process produces fluorocarbon reaction products which formpolymer films on exposed inner surfaces of the chamber roof and sidewalls. We found that, with conventional smooth roof and side wall liner,the polymer deposited on these surfaces began flaking off after thepolymer film reached a thickness of 0.6 to 0.65 mm. The thickness atwhich flaking occurred was independent of changes in process parameters.

EXAMPLE 1 Pyramid Depressions in Aluminum Nitride Roof

[0136] We fabricated a chamber roof (gas distribution plate) as acircular disk of aluminum nitride ceramic, 0.5 inch (13 mm) thick, inwhich we divided the lower circular surface of the roof (the surfaceexposed to the chamber interior) into four quadrants, with fourdifferent surface textures fabricated in the four quadrants. The firstquadrant was smooth, and the second quadrant was bead blasted withsilicon carbide particles.

[0137] The third and fourth quadrants both had the pyramid texture 60 ashown in FIG. 15, with bead blasting subsequently applied to the fourthquadrant but not the third. The dimensions of the pyramid features were:angle θ=45°, height H=0.6 mm, width W=1.5 mm, spacing S=0.6 mm. Wecalculate that the third quadrant had a surface area 30% greater thanthat of the first quadrant due to its pyramid texture. TABLE 1 Example 1Quadrant Pyramid Texture Bead Blasting 1 No No 2 No Yes 3 Yes No 4 YesYes

[0138] We expect that a pattern of square depressions or protrusions 60as shown in FIG. 14 would be preferable to the pyramid-shapeddepressions actually tested, because the square features have a greatersurface area. As stated earlier, we expect that maximizing the surfacearea of the surface contour is advantageous in order to maximize theadhesion of the material deposited thereon.

[0139] We installed the roof in a conventional plasma etch chamber andperformed the same plasma etch process performed in the Control. Wefound that the third quadrant of the roof exhibited the best polymeradhesion. Compared to the smooth first quadrant, we were able to process2.5 times more wafers before material deposited on the third quadrantbegan flaking. At this point, the polymer layer deposited on the thirdquadrant had a thickness of 1.2 mm, which is 85% thicker than themaximum polymer thickness that could be deposited on a conventionalsmooth or bead blasted surface without flaking.

[0140] Because bead blasting conventionally had been used to improveadhesion of deposited material, we were surprised to observe that beadblasting the pyramid textured surface was detrimental to adhesion.Specifically, when we halted the test after depositing 1.2 mm of polymeron the lid, we observed a small amount of flaking from the fourthquadrant, and no flaking whatsoever from the third quadrant. We surmisethat the bead blasting created sharp corners in the surface of the roofthat increased stress in the polymer film, thereby promoting cracks inthe film.

EXAMPLE 2 Different Pyramid Dimensions in Aluminum Nitride Roof

[0141] A second aluminum nitride roof (gas distribution plate) wasfabricated as described for Example 1. The four quadrants were texturedwith pyramids having different dimensions, as summarized in Table 1. Inthe first quadrant, the pyramid dimensions were identical to those ofquadrant 3 of Example 1. In the other three quadrants, the height H ofthe pyramid depressions was increased to 1.1 mm. In quadrants 3 and 4,the angle θ of the pyramid walls relative to the horizontal surface wasdecreased to 30°. In quadrants 2 and 4, the width W and spacing S wereincreased to 2.5 mm and 1.0 mm, respectively. All four quadrantsexhibited no flaking of the polymer deposits. TABLE 2 Example 2 QuadrantAngle θ Height H Width W Spacing S 1 45° 0.6 mm 1.5 mm 0.6 mm 2 45° 1.1mm 2.5 mm 1.0 mm 3 30° 1.1 mm 1.5 mm 0.6 mm 4 30° 1.1 mm 2.5 mm 1.0 mm

EXAMPLE 3 Hemispherical Depressions in Aluminum Oxide Roof

[0142] We fabricated a roof of a 0.5 inch (13 mm) thick plate ofaluminum oxide (alumina) ceramic. Alumina has a much lower thermalconductivity than aluminum nitride, but it has the advantage of beingreadily machinable. We created the pattern of depressions shown in FIGS.16 and 17 by drilling in the alumina an array of approximatelyhemispherical holes, or holes having an arcuate cross section, having ahole diameter W of 4 mm and a spacing S between the perimeters ofadjacent holes of 1 mm. We tested two prototypes in which the depth ofthe holes (the topographical feature height H) were 1 mm and 2 mm,respectively. Both prototypes exhibited no flaking of the polymerdeposits.

EXAMPLE 4 Square Protrusions in Anodized Aluminum

[0143]FIGS. 13 and 14 show an aluminum roof in which we machined anarray of square protrusions. While the section is illustrated as solidthe same features or protrusions may be incorporated into the topceiling 316 having a plurality of gas inlets 350 or mini-gasdistribution plates 220. The aluminum was anodized after the machining.In one prototype the protrusions had 1 mm width W, 1.5 mm height H, and3 mm spacing S. In a second prototype, the protrusions had 2 mm width W,2 mm height H, and 5 mm spacing S. Both prototypes exhibited no flakingof the polymer deposits.

[0144] In the second prototype, we also tested an implementation of thegas inlet holes in the gas distribution plate. Instead of a conventionalarray of gas inlet holes uniformly distributed over the surface of theplate, we installed in the plate only eleven quartz discs (not shown),where each quartz disc was 10 mm diameter and included eleven gas inletholes 0.6 mm diameter.

EXAMPLE 5 Grooves in Anodized Aluminum

[0145]FIGS. 18 and 19 are perspective and sectional views, respectively,of a cylindrical side wall liner 118 composed of anodized aluminum inwhich we machined a series of circumferential grooves 1805 using alathe. Each groove had 1 mm width and 1 mm depth, and adjacent grooveswere spaced apart along the axis of the cylindrical liner by 3 mm. Thealuminum was anodized after the machining.

[0146]FIG. 20 is a perspective view of a similar cylindrical linerhaving both circumferential 1805 and longitudinal 1810 grooves of thesame width, depth, and spacing dimensions stated in the precedingparagraph.

[0147] Both prototypes exhibited no flaking of the polymer deposits.However, the FIG. 20 embodiment is expected to provide superior adhesionbecause its surface area is greater than that of the embodimentsillustrated in FIGS. 18 and 19.

[0148] An advantage of the embodiments of FIGS. 18, 19 and 20 is thatmachining grooves in aluminum typically is less expensive than the otherfabrication methods described earlier.

[0149] While the different textures may be illustrated and describedwith regard to first liner 134 or second liner 118, it is to beappreciated that the textures described herein may be applied to eitheror both liners 134, 118. In alternative embodiments, liner 134 may havea different surface treatment than liner 118. In one specificembodiment, liner 134 may have texture 1605 while liner 118 hascircumferential groove texture 1805.

[0150] V. Plasma Confinement

[0151] Another aspect of the byproduct management feature of the presentinvention is the use of a plasma confinement system to contain theplasma in the processing region 112. Containing the plasma within theprocessing region 112 helps prevent byproduct accumulation in thepumping volume 114. Reducing or eliminating byproduct accumulation inpumping volume 114 reduces the likelihood that byproduct deposition willoccur in and potentially damage pump 109. The plasma confinement featureof the present invention may be better appreciated through reference toFIG. 21.

[0152]FIG. 21 is an enlarged partial view of the etched chamber 100 ofFIG. 1. Lid 102 has been removed for clarity. A vacuum pump 109 exhaustsgases from the processing volume 112 through annular exhaust manifoldand cylindrical pumping channel 138 so as to reduce the total gaspressure in the chamber to a level suitable for the plasma processintended to be performed in the chamber. A throttle valve 8 is mountedwithin the pumping volume 114. The throttle valve 8 regulates the gaspressure within the chamber by controlling the impedance to gas flowwithin the pumping channel 138, thereby controlling the pressure dropacross the pumping channel as required to maintain the desired chamberpressure.

[0153] While described as separate liners, it is to be appreciated thatliners 36 and 38 could be combined into a single liner such as describedabove with regard to liner 118. It is to be appreciated that each of theplasma confinement features described herein with regard to liners 36,and 38 apply to liner 118. It is to be further appreciated that liners36 and 38 are equipped with internal conduits such as conduit 119 ofliner 118 for circulating temperature controlled fluid as describedabove with regard to FIG. 6 and liners 118 and 143.

[0154] The inner liner 38 and the lower half of the outer liner 36respectively function as the inner and outer walls of the annularexhaust volume 114. The annular flange 40 at the bottom of the innerliner 38 includes an arcuate aperture 42, aligned with the cylindricalpumping channel 138, to permit exhaust gases to flow from the annularexhaust manifold, through the flange aperture 42, and then through thecylindrical pumping port 138 to the throttle valve 8 and the pump 109.

[0155] The exhaust channel of the illustrated chamber includes anannular exhaust manifold and a cylindrical pumping channel. The annularexhaust manifold is coaxial with the chamber interior and extends aroundall or most of the azimuth of the chamber interior. The cylindricalpumping channel is coupled to the exhaust manifold at one azimuthalposition. Some conventional plasma chambers include an annular exhaustmanifold coupled directly to the exhaust pump without any intermediatepumping channel. Other conventional plasma chambers couple the pump tothe chamber interior using only a pumping channel that does not extendaround the azimuth of the chamber interior. In this patentspecification, the term “exhaust channel” or “exhaust passage”encompasses either an annular exhaust manifold or a pumping channel, orthe two in combination.

[0156] Exhaust Channel and Magnet for Confining Plasma

[0157] An exemplary embodiment of the invention, shown in FIGS. 21-23,employs two features—a gas flow deflector 522, 516 and a magnet system50—that operate synergistically to prevent the plasma body within thechamber interior from reaching the exhaust pump. In addition to itsbeneficial functions as detailed below, this arrangement assists inproviding high pumping capacity while avoiding polymer deposition in thepumping system. That is, as explained in the present disclosure, onefeature of the inventive chamber is the high flow pumping capability forreduced residence time of the gas molecules. However, for maintenancereasons, it is advisable to constrain or limit the plasma from reachingto the pumping area of the chamber. The arrangement described belowassists in achieving this goal.

[0158] Specifically, the interior of the exhaust manifold 30 includes atleast one deflector 522, 516 that deflects at least a substantialportion of the exhaust gases transversely, instead of allowing all ofthe exhaust gases to flow in an unobstructed straight path through theexhaust manifold. (By “transversely” we mean perpendicular to thedirection of the path along which the gases would flow in the absence ofthe deflector.)

[0159] The deflector creates turbulence in the flow of exhaust gasesthat increases the rate of collisions of reactive species in the gaseswith the deflector and with the walls of the exhaust manifold near thedeflector. The collisions promote surface reactions among the reactivespecies so as to produce deposits on the walls. This depletes theexhaust gases of the reactive species that tend to produce suchdeposits, thereby greatly reducing or eliminating the concentration ofsuch reactive species in the exhaust gases downstream of the deflector,and therefore greatly reducing or eliminating undesirable deposits onthe throttle valve 8 and pump 109.

[0160] The deflector also increases the rate of collisions of chargedparticles in the exhaust gases so as to promote recombination of suchcharged particles, thereby reducing the concentration of chargedparticles in the exhaust gases.

[0161] Additionally, a magnet system 50 (52-57) is positioned near thedeflector 522, 516 so as to produce a magnetic field within the exhaustmanifold near the deflector. The magnetic field preferably has asubstantial component directed transverse to the direction of exhaustgas flow through the manifold. The transverse component of the magneticfield transversely deflects moving electrons so that they are morelikely to recombine with positive ions, thereby reducing theconcentration of charged particles in the exhaust gases.

[0162] Since the deflector and the magnetic system both reduce theconcentration of charged particles in the exhaust gases, the two incombination can reduce the concentration sufficiently to extinguish theplasma downstream of the deflector and magnet system. Specifically, themagnetic field should be strong enough, and the turbulence caused by theone or more deflectors should be great enough, so that the combinedeffects of the magnetic field and the deflector prevent the plasma bodywithin the chamber from reaching the throttle valve 8 and exhaust pump109.

[0163] The plasma confinement effect of the magnetic field permits theuse of a wider and/or less sinuous exhaust channel than would berequired to block the plasma without the magnetic field. Therefore, thepressure drop across the exhaust channel can be reduced in comparisonwith prior art designs that rely entirely on the sinuousness of theexhaust manifold to block the plasma.

[0164] In the embodiment shown in FIGS. 21-23, the deflector consists oftwo coaxial, annular protrusions 522, 516 extending into the gaspassageway of the exhaust manifold 30 from the walls of the manifold.The upper protrusion 522 extends radially inward from the outer liner36, and the lower protrusion 516 extends radially outward from the innerliner or cathode shield 38. Because the two protrusions overlap eachother radially, they do not permit any of the exhaust gases to travel ina straight line through the exhaust manifold, thereby maximizing thelikelihood that reactive species in the exhaust gases will collide witheither the protrusions or the walls of the exhaust manifold.

[0165] We define a “magnet system” as one or more magnets in combinationwith zero, one or more magnetically permeable pole pieces to form amagnetic circuit having a north pole and a south pole. In the embodimentof FIGS. 21-23, the magnet system 50 consists of two annular magnets 52,53 mounted coaxially with the annular exhaust manifold 30 and spacedapart along the axis of the manifold. The two annular magnets areidentical, except that the first magnet 52 has its north and south polesat its radially inner and outer ends, respectively, whereas the secondmagnet 53 has its north and south poles at its radially outer and innerends, respectively. The magnet system 50 also includes a cylindrical,magnetically permeable pole piece 54 mounted coaxially with the twomagnets 52, 53 so as to abut and extend between the radially inner endsof the two magnets, thereby completing a magnetic path or “magneticcircuit” between the two magnets.

[0166] Consequently, the north pole 56 of the magnet system 50 is thenorth pole of the first annular magnet 52, i.e., the pole of the firstmagnet opposite the pole that abuts the pole piece 54. The south pole 57of the magnet system 50 is the south pole of the second annular magnet53, i.e., the pole of the second magnet opposite the pole that abuts thepole piece 54.

[0167] The magnet system 50 preferably is mounted within the lowerprotrusion 516 so that the ends of the north and south poles 56, 57 ofthe magnet system are as close as possible to the narrow portion of thegas passageway within the exhaust manifold that is radially outward ofthe protrusion. Mounting the magnet system close to the narrowestportion of the exhaust manifold passageway is desirable to maximize themagnetic field strength to which the exhaust gases are subjected.

[0168] An exemplary implementation of the magnet system just describedhas a U-shaped cross section as shown in FIGS. 21-23, with the base ofthe “U” pointing radially inward and the open end of the “U” pointingradially outward. More specifically, the shape of the magnet system isthat of a U-shaped horseshoe magnet that is revolved around thelongitudinal axis of the chamber.

[0169] The magnetic field pattern produced by this U-shaped magnetsystem, represented by field line 58 in FIG. 22, is desirable because itis concentrated primarily within the passageway of the exhaust manifold.This concentration has at least two advantages. One advantage is that,as stated above, it maximizes the magnetic field strength to which theexhaust gases are subjected, thereby maximizing the effectiveness of themagnet in extinguishing the plasma downstream of the magnet.

[0170] A second advantage of the U-shaped magnet system is that themagnetic field strength declines rapidly along the longitudinal axis ofthe chamber, so that the magnetic field strength is low at the workpiece10. To minimize the risk of damaging the workpiece by ion bombardment orelectrostatic charge accumulation, the magnetic field strength at theworkpiece 10 should be as low as possible, preferably no greater than 5gauss, and more preferably no greater than 3 gauss. The magnet system ismounted in the lower protrusion 516 rather than the upper protrusion 522in order to position the magnet system as far as possible from theworkpiece 10, thereby minimizing the strength of the magnetic field atthe workpiece 10.

[0171]FIG. 24 shows an alternative magnet system 60 whose magnets andpole pieces are interchanged relative to the embodiment of FIGS. 21-23.Specifically, the upper and lower annular members 62, 63 aremagnetically permeable pole pieces rather than magnets. The cylindricalmember 64 is a magnet rather than a pole piece, the cylindrical magnethaving a north magnetic pole at the upper end of its longitudinal axisabutting the upper pole piece 62 and a south magnetic pole at the lowerend of its axis abutting the lower pole piece 63.

[0172] A possible alternative implementation of the exhaust manifoldcould omit the upper protrusion 522, relying on the combination of thelower protrusion 516 and the magnet system 50 to block the plasma.

[0173] Another alternative exhaust manifold design would omit the lowerprotrusion 516 (which extends radially outward from the inner liner 38)and substitute a modified magnet system 51, shown in FIG. 25, that ismounted within the upper protrusion 522 (which extends radially inwardfrom the outer liner 36). The north and south magnetic poles 56, 57 ofthe modified magnet system 51 should be adjacent the gas passageway atthe radially inner end of the protrusion 44. This can be accomplishedusing the same magnets 52, 53 and pole piece 54 as in the FIG. 23 magnetsystem, but with the pole piece 54 moved from the radially inner end tothe radially outer end of the two magnets, as shown in FIG. 25.

[0174]FIG. 26 shows an alternative magnet system 61 that differs fromthe FIG. 25 magnet system 51 in that the magnets and pole pieces areinterchanged. (See the discussion of the FIG. 24 embodiment above.)

[0175] We also tested the exhaust manifold design shown in FIG. 27 in aplasma chamber that otherwise was identical to the chamber shown in FIG.21. The exhaust manifold of FIG. 27 includes upper and lower annularmagnets 68, 69 mounted within the upper and lower protrusions 522, 516,respectively, of the exhaust channel 30. The upper magnet 68 has northand south poles at its radially inner and outer ends, respectively. Thelower magnet 69 has north and south poles at its radially outer andinner ends, respectively. Consequently, the north and south poles of theupper magnet are aligned with the south and north poles of the lowermagnet. The resulting magnetic field, depicted by magnetic field lines70, is highly concentrated in the region of the exhaust manifold channelor passageway between the two protrusions. As explained in the precedingdiscussion of the FIG. 21 embodiment, such concentration is desirable tomaximize the strength of the magnetic field to which the exhaust gasesare subjected and to minimize the magnetic field at the workpiece 10.

[0176] To facilitate testing the FIG. 27 embodiment with different gapsbetween upper and lower protrusions 522, 516, our prototype included anannular dielectric spacer 72 below the outer dielectric liner 36. Bysubstituting a thicker spacer 72, we could increase the height of theupper protrusion 522 and thereby increase the gap between the twoprotrusions. We used the same magnets 68, 69 for every spacer thicknesswe tested. Therefore, when we substituted a thicker spacer, we bothincreased the gap and decreased the magnetic field strength in the gap.

[0177] In these tests we found that the plasma was successfully blockedfrom extending below the lower protrusion when the gap between the upperand lower protrusion was 0.5 inch or less and the magnetic fieldstrength in the gap was at least 100 or 150 gauss. We also found that,in the illustrated chamber, the magnetic field strength declined fastenough away from the magnets so that the magnetic field strength at theworkpiece 10 was less than 3 gauss, which we consider low enough toavoid risk of damage to the workpiece However, when we tested a widergap between the two protrusions, and therefore a lower magnetic fieldstrength in the gap, we found that the plasma was not successfullyblocked.

[0178] We currently prefer the FIG. 21 embodiment because moremanufacturing labor is required to mount magnets within two protrusionsas in the FIG. 27 design in comparison with mounting magnets in only oneprotrusion as in the FIG. 21 design.

[0179] Another alternative embodiment of the exhaust manifold would beto omit one protrusion and its corresponding magnet from the FIG. 27embodiment. We tested a prototype that was identical to the one shown inFIG. 27, except that the upper protrusion 522 and the upper magnet 68was omitted leaving only the lower protrusion and magnet as illustratedin FIG. 28. While this prototype successfully, blocked the plasma fromextending below the lower protrusion, we considered the magnetic fieldat the workpiece to be undesirably strong. However, this embodimentmight be suitable for use in semiconductor fabrication processes inwhich the workpiece is not overly susceptible to damage by ionbombardment or electrostatic charge accumulation.

[0180] More generally, the deflector 522, 516 need not be one or moreprotrusions extending from the walls of the exhaust channel, but can beany structure within the exhaust channel that causes substantialturbulence in the exhaust gases. As described earlier, such turbulencewill promote recombination of charged particles so as to help extinguishthe plasma downstream of the turbulence, and it will promote surfacereactions among reactive species so that reaction products will bedeposited on surfaces near the deflector rather than on pumpingcomponents 8,109 downstream.

[0181] The deflector and magnet system can be mounted in any part of theexhaust channel, such as the pumping channel 32, even though they aremounted in the annular exhaust manifold in the preferred embodiment.

[0182] Of course, any materials between the magnet system and theinterior of the exhaust channel should be non-magnetic so as to avoidblocking the magnetic field from reaching the exhaust gases. As statedearlier, in the preferred embodiment the protrusions in which the magnetsystem is mounted are anodized aluminum.

[0183] To equalize the exhaust gas flow rate around the azimuth of thechamber, it is preferable to slightly reduce the radial width of theexhaust manifold near the azimuth of the pumping channel and to slightlyincrease its radial width near the opposite azimuth, i.e., near theazimuth 180 degrees away from the pumping channel.

[0184] The directions of the magnetic fields can be reversed withoutaffecting the operation of the invention. Therefore, all references tonorth and south poles can be interchanged.

[0185] The illustrated plasma chamber has circular symmetry because itis intended for processing a a single, circular semiconductor wafer. Inplasma chambers having other geometries, such as chambers for processingmultiple substrates or rectangular substrates, the components of theinvention such as the deflector and magnet system would be expected tohave rectangular or more complex geometries. The term “annular” as usedin this patent specification is not intended to limit the describedshape to one having a circular inner or outer perimeter, but encompassesrectangular and more complex shapes.

VI. Alternative Chamber Embodiments of the Present Invention

[0186]FIG. 28 is a cross sectional view of a capacitively coupled,Magetically Enhanced Reactive Ion Etch (MERIE) chamber havingembodiments of the improvements of the present invention. FIG. 28illustrates an etch processing system 2800 similar having the samesystems as processing system 50 of FIG. 1. Etch processing system 2800includes MERIE chamber 2850. MERIE chamber 2850 is similar to chamber100 described above with the inclusion of a number of pairedelectromagnets. For example, four electromagnets 2810, 2812, 2814, and2816, typically mounted in a generally rectangular array, one each onthe alternating walls of chamber sidewall 106 each having a suitablepower supply 2830, 2832, 2834 and 2836. For clarity, only electromagnets2810 and 2812 and their respective power supplies 2830 and 2832 areillustrated in FIG. 28. Under the control of controller 140, the coilpairs 2810 and 2812 and 2814 and 2816 cooperatively provide aquasi-static, multi-directional magnetic field which can be stepped orrotated about the wafer 10. Electromagnets 2810, 2812, 2814 and 2816generate a controllable magnetic field with a magnitude from about 0Gauss to about 150 Gauss. Also, the magnitude of the magnetic field canbe adjusted to select etch rate and vary ion bombardment. Additionaldetails of MERIE chamber operation are provided in commonly assignedU.S. Pat. No. 4,842,683 entitled, “Magnetic Field-Enhanced Plasma EtchReactor.”

[0187]FIG. 28 also illustrates an alternative embodiment of the secondliner 118 having only the lower protrusion 516. Magnetic confinementsystem 52 is disposed within lower protrusion 516. While the magneticconfinement system 52 is illustrated, it is to be appreciated that anyof the magnetic confinement systems described above in the sectionentitled “Plasma Confinement” may be modified for use in the singleprotrusion embodiment of the liner 118.

[0188]FIG. 29 is a cross sectional view of another type of etch chamberhaving embodiments of the present invention. FIG. 29 illustrates an etchprocessing system 2900 having an etch processing chamber 2950.Processing system 2900 is similar to processing system 50 of FIG. 1 withthe addition of a second RF generator 2910 and impedance matchingcircuits 2915. Processing chamber 2950 is similar to processing chamber100 with the addition of parallel plate 2920. In operation, RF signalsfrom RF generators 150 and 2910 are provided under the control ofcontroller 140, via impedance matching circuitry 151 and 2915,respectively, to electrode 105 and parallel plate electrode 2920,respectively. In one alternative embodiment, RF generators 150 and 2920provide RF signals at the same frequency. In an alternative embodiment,RF generators 150 and 2920 provide RF signals at different frequencies.

[0189]FIG. 30 is a cross sectional view of another processing chamberincorporating embodiments of the present invention. FIG. 30 illustratesan etch processing system 3000 having a magnetically enhanced etchchamber 3050. Processing system 3000 is similar to processing system 50with the addition of controller 140 operating a magnetic fieldgenerating mechanism 3010. Processing chamber 3050 is similar toprocessing chamber 100 with the addition of the magnetic fieldgenerating mechanism 3010. The magnetic field generating mechanism 3010is disposed on the outer peripheral surface of the cylindrical wall 106of the process chamber 3050. The magnetic field generating mechanism3010 comprises a plurality of circumfrentially arranged permanentmagnets having a predetermined polarity which enables generation of amagnetic field parallel to the upper surface of the wafer 10, and adriving mechanism for revolving the magnets around the processingchamber 3050. The magnetic field generating mechanism 3010 generates arotational magnetic field, which rotates about the vertical center axisof the process chamber 3050 or of the wafer 10, in the processing volume112 region. Additional details regarding the magnetic field generatingmechanism 3010 is disclosed in, for example, U.S. Pat. No. 5,980,687.

[0190]FIG. 31 is a cross sectional view of another processing chamberincorporating embodiments of the present invention. FIG. 31 illustratesan etch processing system 3100 having an etch chamber 3150. Processingsystem 3100 is similar to processing system 50 with the addition of asecond RF generator 3110 and impedance matching circuitry 3105 operatedby controller 140. Processing chamber 3050 is similar to processingchamber 100 with the addition of modifications to lid 102 to accommodateantenna 3115 mounted to the lid 102 and acting as an inductive memberfor coupling RF power from RF generator 3110 into processing volume 112.Impedance matching circuitry 3105 couples the RF signal from generator3110 to antenna 3115. Nozzles 350 have been positioned at the peripheryof lid 102 to accommodate the efficient inductive coupling of rf energyfrom antenna 3115 to a plasma formed in processing volume 112. FIG. 31illustrates antenna 3115 in a flat coil arrangement. Other arrangementsof antenna 3115 are possible, such as, for example, a ring arrangement,spiral arrangement, stacked arrangement, or, additionally, multipleantenna segments could be employed with each antenna segment of amultiple antenna segment coupled to an r.f.generator.

[0191]FIG. 32 is a cross sectional view of another embodiment of an etchchamber having the improvements of the present invention. FIG. 32illustrates an etch processing system 3200 having an etch chamber 3250.Processing system 3200 is similar to processing system 50 of FIG. 1 withthe addition of the second RF generator 3204 and impedance matchingcircuit 3206. Etch chamber 3250 is similar to etch chamber 100 with theaddition of a flat inductive coil 602 and a showerhead style gasinjection system instead of injector nozzles 350. The etch chamber 3250has a temperature controlled chamber liner 104 which regulates thetemperature of the chamber liner 104 in the manner described above. Thechamber 3250 has a lid assembly 3208 that, with the chamber walls 106and chamber bottom 108, define the process volume 110. A showerhead 3212is disposed beneath the lid assembly 3208. Process and other gases froma gas panel 105 pass through a passage in the lid assembly 3208 and aredispersed into the chamber volume 110 through a plurality of holes inthe showerhead 3212. Although shown with a first liner 118 and a secondliner 134, the etch chamber 3250 may comprise one or both of the firstand second liners 118 and 134. Etch chamber 3250 also illustrates aliner 118 having only a single protrusion 516 with magnetic system 50disposed therein.

VII. Chamber Process Window and Representative Critical Dielectric EtchProcesses

[0192] Embodiments of the improvements of the present invention provideexpanded dielectric etch processing capability. The dielectric etchprocess window enabled by combining the various improvements surpassesthe dielectric etch window enabled by conventional etch chambers.

[0193] For example, a magnetically enhanced reactive ion etch chamberhaving embodiments of the present invention, such as, for example, MERIEchamber 2800 of FIG. 28, has several processing advantages overconventional MERIE processing reactors. Since it is not uncommon fordielectric etch processes to generate polymeric byproducts, severalaspects of the present invention cooperatively provide improved polymeradhesion control. First, direct temperature control liners on the wallsand cathode help minimize the heating effects caused by plamsa cycling.Plasma cycling occurs when the plasma heats portions of the chamberduring processing. Polymer adhesion generally decreases with increasingtemperature. As a result, those areas heated by plasma cycling are morelikely to have polymer depositions that tend to flake off and causeparticle contamination. By controlling and uniformly reducing thetemperature of the liners, adhesion of the polymeric byproducts to theliners is improved thereby reducing the likelihood that the polymerbyproducts will flake off and form particles. Second, use of minimizedsize gas inlet nozzles 350 ensures that the nozzles are heated by theplasma to temperatures above which the likelihood that by products willform on or adhere to the nozzle openings is reduced. Another advantageof minimized gas inlet nozzles 350 is that because of the small gasinlet nozzle area most of the plasma and by products contact thetemperature controlled lid. Like the byproducts that come into contactwith the temperature controlled liners, byproducts contacting thetemperature-controlled lid will also preferentially deposit on andadhere to the temperature controlled lid and not on the plasma heatedminimized size gas distribution nozzles. Third, the cathode and walltemperature controlled liners and the temperature-controlled lid mayalso further improve byproduct adhesion by incorporating surfacetexturing features such as those described above in Section IV. Thus,the combination of temperature controlled wall and cathode liners andtemperature controlled lid together with minimized gas inlets ensuresthat most of the plasma processing region comprises temperaturecontrolled surfaces with, preferably, high adhesion texturing.

[0194] Processing chambers having embodiments of the present inventionenable dielectric etch processes employing high magnetic fields as highas about 120G and RF energy up to about 2500 W. Embodiments having ahigh chamber volume, such as a chamber volume of about 25,000 cc, andhigh capacity vacuum pumping systems such as, for example, a pump systemhaving a pumping speed of from about 1600 l/s to about 2000 l/s enable ahigh gas flow-low chamber pressure processing regime that is notavailable in conventional magnetically enhanced and reactive ion etchprocessing reactors. One advantage of the high pumping speed is animproved capability to control reactive species formation and residencetime. Residence time is directly related to the amount of reactive gasdissociation occurring in the plasma. The longer a gas molecule remainsexposed to a plasma, the more likely it is that dissociation of that gasmolecule will continue. Thus, etch processing reactors havingembodiments of the present invention provide desirable plasma gascompositions by enabling improved residence time control.

[0195] Attempts have been previously made and reported on the use ofC₄F₆ for dielectric etch processes. However, these reports have taughtaway from using a parallel plate reactor, such as the reactor of thepresent invention, for dielectric etch using C₄F₆, especially for thelinear form of C₄F_(6,) e.g., hexafluoro-1, 3-Butadiene (CF2=CFCF═CF2).Moreover, for the best knowledge of the inventors, none of the reportedattempts have been successfully transferred into production lines.

[0196] For example, Yanagida discloses the use of a chain,hexafluorocyclobutene (c-C₄F₆), rather than linear (C₄F₆) in U.S. Pat.No. 5,338,399. On the other hand, in U.S. Pat. No. 5,366,590, Kadamurasuggests that either linear of chain C₄F₆ may be used, but that a highdensity plasma, such as that generated using ECR plasma source,inductively coupled plasma source, or transformer coupled plasma source,must be used with either gas. Similarly, in Japanese Application Hei9[1997]-191002 Fukuda discloses his work with linear C₄F₆, also usinghigh density plasma generated using ECR plasma source. Chatterjee etal., report their work with hexafluoro-2-buttyne and hexafluoro-1,3-Butadiene, also using high density plasma generated by inductivelycoupled plasma source. Evaluation of Unsaturated Fluorocarbons forDielectric Etch Applications, Ritwik Chatterjee, Simon Karecki, LauraPruette, Rafael Reif, Proc. Electrochem. Soc. PV 99-30 (1999). Thus, theprior art teaches that in order to achieve acceptable etch results usinglinear C₄F₆, such as hexafluoro-1, 3-Butadiene, one should use highdensity plasma, and not low or medium density plasma, such as thatachieved using a capacitively coupled plasma source.

[0197] However, the present inventors have shown admirable results ofetching using linear C₄F₆ in a capacitively coupled plasma source of theinvention. The present inventors believe that the high energy generatedby high density plasma chambers causes excessive dissociation of thelinear C₄F₆. Therefore, they believe that improved results can beachieved using a capacitively coupled chamber, so as to limit thedissociation of the molecules. Also, the present inventors further limitdissociation by using the high pumping capacity enabled by the inventiveetch chamber.

[0198] While not desiring to be bound by theory, it is believed that asan etchant gas, such as for example, linear C₄F₆, enters the plasmaregion of a processing chamber and is exposed to the plasma, it iscracked or dissociated into smaller entities. Generally, forfluorocarbon process gases, shorter residence times provide a capabilityto produce an increased percentage of the desirable fluorocarbon radicalCF_(x)* while longer residence times produce an increased fraction ofthe fluorine radical F*. Too much fluorine radical production may reducephotoresist selectivity and/or reduce sidewall profile control.Applicants have found that photoresist selectivity is generally improvedwith a residence time of less than about 70 ms, and preferably aresidence time of less than about 50 ms. Applicants have found thatoxide etch rate is improved with a residence time of about 40 ms. Suchresidence time is made possible by the processing reactor of the presentinvention and enables etching using linear C₄F₆ in a capacitivelycoupled RIE mode.

[0199] Another useful method of controlling the degree of radicalformation in a gas composition is by incorporating an inert gas into thereactive gas composition. It is believed that increasing the amount ofinert gas in a reactive gas composition reduces the amount of radicalsformed from the reactive gas when the reactive gas/inert gas mixture isexposed to a plasma. Inert gas flow rate to reactive gas flow rateratios from about 5:1 to about 20:1 are preferred. Total gas flows fromabout 50 sccm to about 1000 sccm with inert gas flow to reactive gasflow ratios of between about 12:1 to about 16:1 being more preferred.

[0200] Dielectric etch chambers having embodiments of the presentinvention enable a dielectric etch process window comprising up to 2500W RF power, magnetic fields from about 0 to about 150 Gauss, total gasflows from 40 sccm to 1000 sccm, chamber pressures from about 20 mT toabout 250 mT and liner temperatures ranging from about −20° C. to about50° C. As described below with regard to FIGS. 33-38, the expandedprocess window enabled by etch reactors having embodiments of thepresent invention provide improved dielectric etch process performance,reliability and process tuning versatility for a wide variety ofcritical dielectric and oxide etch applications.

[0201] A representative self-aligned contact feature is illustrated inFIGS. 33A and 33B, which are not to scale. FIG. 33A represents pre-etchself aligned contact structure 3300. FIG. 33B represents post etchself-aligned contact structure 3305. Both self aligned contactstructures 3300 and 3305 are formed on a silicon substrate 3310.Generally, word lines 3315 typically comprise and oxide layer 3316, aWSi_(x) layer 3317 and a polysilicon layer 3318. Word lines 3315 arecovered by a liner layer 3320 that is typically formed from siliconnitride. A representative bitline region 3325 is illustrated betweenadjacent word lines 3315. Dielectric layer 3330 is formed over linerlayer 3320 and is typically formed from a silicon dioxide, such as, forexample, and oxide layer formed from O₃-TEOS based processes.Alternatively, the dielectric layer 3330 may be formed from a dopedsilicon oxide film, such as, for example, a boron and phosphorus dopedsilicon glass (BPSG). Self aligned contact feature 3300 may includeother layers, such as, for example, an anti-reflective coating may beutilized between pattern layer 3335 and dielectric layer 3330.

[0202] Also illustrated in pre-etch self-aligned contact feature 3300 ofFIG. 33A is a mask pattern layer 3335. When pre-etch self alignedcontact feature 3300 is exposed to a suitable etch process, dielectriclayer 3330 is etched thereby transferring the pattern of mask layer 3335onto the dielectric layer 3330. As illustrated in FIG. 33B, a contactarea 3340 is formed when a portion of dielectric layer 3330 adjacentcontact region 3325 is removed.

[0203] The exact dimensions of the self aligned contact structure 3300and 3305 will vary depending upon a number of considerations, such asfor example, device application, to design rules and critical dimensionsof contact area 3340. For example, for purposes of illustration and notlimitation, the self aligned contact structure 3300 may be a 0.25 microndesign rule device having an overall dielectric layer 3300 thickness ofabout 6000 angstroms, a liner layer 3320 thickness of about 650angstroms and a mask layer 3335 thickness of more than about 7000angstroms with a pattern opening of about 0.25 microns. The self alignedcontact etch processes enabled by the present invention are capable ofetching self-aligned contacts having design rules with criticaldimensions of less than about 0.25 microns and preferably havingcritical dimensions of between about 0.1 microns and to less than about0.18 microns.

[0204] Etching of a self-aligned contact feature is a criticaldielectric etch application in part because of the need to avoid etchstop or residual oxide at the word line sidewall. Additionally, asuitable self aligned contact etch process must maximize selectivity tothe nitride shoulder 3345. Preferably, nitride shoulder selectivity isgreater than about 20:1.

[0205] A suitable self aligned contact etch process chemistry comprisesa fluorocarbon gas, and an oxygen comprising gas and an inert gas wherethe total gas flow is more than about 700 sccm and the inert gascomprises more than about 90% of the total gas flow. Reactive gas ratiorefers to the ratio of the inert gas flow to the reactive gas flow. Inthis example, reactive gas ratio would be the ratio of the inert gasflow rate to the combined gas flow rates of the fluorocarbon gas and theoxygen comprising gas. A suitable self-aligned contact etch process hasa reactive gas ratio of from about 12:1 to about 16:1 with a preferredreactive gas ratio of about 14.5:1. In a specific embodiment, the ratioof the flow rate of the fluorocarbon gas to the flow rate of the oxygencomprising gas is from about 1.5:1 to about 2:1. The chamber pressure ismaintained from about 30 mT to about 40 mT, RF power is maintained fromabout 1800W to about 2000 W, the magnetic field is about 50G and theetch chamber is exhausted at a rate of from about 1600 l/sec to about2000 l/sec. In a specific preferred embodiment, the etch chamber isexhausted at a rate of from about 48 chamber volumes to about 80 chambervolumes per second. In another preferred embodiment, the substratesupport or cathode is maintained at between about 15° C. to about 20° C.while the temperature of a wall or, preferably a temperature controlledliner adjacent the substrate is maintained at about 50° C. In aspecific, preferred embodiment the fluorocarbon gas is C₄F₆, the oxygencomprising gas is O₂ and the inert gas is Ar.

[0206] A representative high aspect ratio dielectric etch process willnow be described with reference to FIGS. 34A and 34B. FIG. 34Aillustrates a pre-etch high aspect ratio structure 3400 and FIG. 34Billustrates a post etch high aspect ratio structure 3405. Neitherstructure 3400 nor 3405 are illustrated to scale. In this context, ahigh aspect ratio dielectric etch process is defined as etching featureshaving aspect ratios greater than about 5:1 to about 6:1 while a veryhigh aspect ratio process is defined as etching features having aspectratios in the range of from about 10:1 to about 20:1. For example, theaspect ratio of the feature 3430 in FIG. 34B is the ratio of thedielectric layer thickness 3422 to the feature width 3426. Magneticallyenhanced and reactive ion etch chambers having embodiments of thepresent invention are capable of etching both high and very high aspectratio features.

[0207] Turning now to FIG. 34A, a representative pre-etch high aspectratio structure 3400 is illustrated that comprises a stop layer 3415formed over a silicon substrate 3410. A dielectric layer 3420, having athickness 3422, is formed over the stop layer 3415. A mask layer 3425 isformed over the dielectric layer 3420. Stop layer 3415 could be formedfrom a suitable stop layer material, such as silicon nitride forexample. Of course, the specific type of stop layer material will dependupon the device type and design rules of a particular device.

[0208]FIG. 34B illustrates post etch high aspect ratio structure 3405comprising high aspect ratio feature 3430. High aspect ratio feature3430 is formed in the dielectric layer 3420 by transferring the patternof mask layer 3425 onto dielectric layer 3420. The pattern of mask layer3425 is transferred onto dielectric layer 3420 by conducting a suitablehigh aspect ratio dielectric etch process in and etch processing reactorhaving embodiments of the present invention as described in greaterdetail below. While a specific feature width 3426 will vary dependingupon design rules, in general, feature width 3426 varies from about 0.25micrometers to about 0.1 micrometers. The feature depth corresponds tothe thickness of dielectric layer 3420.

[0209] As dielectric layer thickness 3422 increases, the selectivity ofthe high aspect ratio dielectric etch process to the mask layer 3425photoresist material becomes even more critical. The possibility of etchstop also increases with increasing dielectric layer thickness 3422.Shrinking feature width 3426 also poses challenges for maintaining anappropriate sidewall profile of contact 3430. Bowing or a re-entrantsidewall profile of contact 3430 can lead to an unacceptably smalldiameter at the bottom of contact 3430 adjacent stop layer 3415. Highaspect ratio contact etching is a critical dielectric etch processbecause of the challenges posed by shrinking feature width, increasingcontact depth, selectivity to photoresist materials and sidewall profilecontrol.

[0210] High aspect ratio feature etching may also be complicated by adielectric layer 3420 comprising a doped silicon oxide such as, forexample, BPSG. Dielectric layers 3420 comprising a plurality ofdielectric materials forming a multilevel structure also pose manychallenges to high aspect ratio feature etching. One example of such amultilevel structure is a feature structure having a dielectric layer3420 comprising multiple intermediate stop layers at different depths,such as for example, those features seen mainly in the peripheral areasof stack capacitor DRAM structures.

[0211] The exact dimensions of the high aspect ratio structure 3400 willvary depending upon a number of considerations, such as for example, thedevice application, and the design rules of a particular device. Forexample, the representative high aspect ratio structure 3400 may have amask with 3426 of about 0.25 microns, a mask layer 3425 thickness ofabout 7000 angstroms, a dielectric layer thickness 3422 of about 15,000angstroms and a stop layer 3415 thickness of about 500 angstroms. It isto be appreciated that the above specific dimensions or for illustrationand not for limitation. Magnetically enhanced and reactive ion etchchambers having embodiments of the present invention are capable ofetching high aspect ratio and very high aspect ratio features havingaspect ratios from about 5:1 to about 20:1 with critical dimensions(i.e., contact with 3426, for example) of from about 0.25 microns toabout 0.1 microns.

[0212] Suitable high aspect ratio dielectric feature etch process windowthat meets the above challenges includes high magnetic field of up toabout 100G, high RF power of up to about 2000W and high inert gas flowof between about 500 sccm and about 1000 sccm. Increased magnetic fieldprovides increased selectivity to the photomask material in the masklayer and reduces the likelihood of sidewall bowing. Increased inert gasflow provides a wider range of reactive gas dilution thereby decreasingresidence time and reactive species formation which in turn furtherimprove photoresist selectivity. In addition, the increased pump speedsof the present invention described above with regard to self alignedcontact etching may also be employed in high aspect ratio etching tofurther improve control of residence time and reactive species aformation.

[0213] The suitable high aspect ratio dielectric etch process comprisesa fluorocarbon gas, and oxygen comprising gas and an inert gas where thetotal gas flow is more than about 700 sccm an and the inert gascomprises more than about 90 percent of the total gas flow. A suitablehigh aspect ratio dielectric etch process has a reactive gas ratio offrom about 10:1 to about 15:1. In a specific embodiment, the ratio ofthe flow rate of the fluorocarbon gas to the flow rate of the oxygencomprising gas is about 1.5:1. In a specific embodiment the gascomposition used for etching comprises a fluorocarbon gas flow thatprovides from about 3 percent to about 6 percent of the total gas flow,an oxygen comprising gas comprising from about one percent to about fourpercent of the total gas flow and an inert gas making up more than 90percent of the total gas composition flow.

[0214] In the specific embodiment, the chamber pressure is maintainedfrom about 20 mT to about 60 mT, the RF power is from about 1,000 wattsto about 2,000 watts, the magnetic field is maintained at about 100G,and the etch chamber is exhausted at a rate from about 48 chambervolumes to about 80 chamber volumes per second. In another preferredembodiment, the substrate support is maintained at about −20 degrees C.while a wall or preferably, direct temperature control liner, ismaintained at about 15C. In a specific preferred embodiment, thefluorocarbon gas is C₄F₆, the oxygen comprising gas is O₂ and the inertgas is argon.

[0215]FIGS. 35A and 35B illustrate, respectively, representative pre-andpost-metal via etch structures 3500 and 3505. Generally, metal via etchprocesses are important in forming interconnect structures between metallayers in an electronic device. Typically, the via formed in thedielectric material during a metal via etch is later filled by a metalsuch as, for example, a tungsten plug commonly used in aluminum basedmetalization schemes. Suitable metal via etch processes are selective tothe barrier layer 3515 or alternatively, selective to the underlyingmetal layer 3510.

[0216]FIG. 35A represents pre-etch metal via fill structure 3500 formedover metal layer 3510. A barrier layer 3515, such as for example, alayer comprising titanium and titanium nitride, is formed over metallayer 3510 and separates dielectric layer 3520 from metal layer 3510.The dielectric layer 3520 is typically a TEOS based silicon dioxide andmay, alternatively, be an HDP-CVD silicon dioxide film as well. FIG. 35Aalso illustrates the use of an anti-reflective coating layer 3525 undermasking layer 3530.

[0217] The specific dimensions of metal via etch structures 3500 and3505 such as the thickness of dielectric layer 3520 and the width ofcontact via 3535 vary depending upon the type of via structure and uponthe design rules used in a particular device. For example, the 0.25micron feature device may have a dielectric layer 3520 about 10,000angstroms thick and formed from TEOS with a barrier layer 3515 about 500angstroms thick and formed from titanium nitride. Etch reactors havingembodiments of the present invention are capable of etching contact viashaving critical dimensions of from about 0.25 microns to about 0.1microns and vias having aspect ratios of up to about 5:1.

[0218] A suitable metal via etch gas composition chemistry comprises afluorocarbon gas, and an oxygen comprising gas and an inert gas whereinthe total gas flow is less than about 500 sccm. In a particularembodiment, the inert gas flow rate provides about 85 percent of thetotal gas composition flow and the ratio of the inert gas to thereactive gases (i.e., the ratio of the inert gas flow rate to thecombined flow rates of the fluorocarbon gas and the oxygen comprisinggas) is between about 4:1 to about 6:1. In a specific preferredembodiment, the fluorocarbon gas provides about 9.5 percent of the totalgas composition flow, the chamber is maintained at about 20 mT, the RFpower is about 1500 watts, the magnetic field is about 50 Gauss and thesubstrate support and a wall, or preferably a temperature control lineradjacent the substrate support, are maintained at about the sametemperature.

[0219] In an alternative embodiment, the gas composition for a metal viaetch process comprises a first fluorocarbon gas having a carbon tofluorine ratio of 1:3, a second fluorocarbon gas having a carbon tofluorine ratio of about 2:1 and any inert gas wherein the total gas flowof the gas composition is from about 200 sccm and to about 300 sccm. Ina specific preferred embodiment, the first fluorocarbon gas comprisesfrom about 14 percent to about 18 percent of the total gas compositionflow, and the second fluorocarbon gas comprises from about 13 percent toabout 16 percent of the total flow of the gas composition. In a specificpreferred embodiment, the ratio of the first fluorocarbon gas flow rateto the inert gas flow rate and the ratio of the second fluorocarbon gasflow rate to the inert gas flow rate is from about 0.2 to about 0.25. Inanother specific embodiment, the first fluorocarbon gas is C₂F₆, thesecond fluorocarbon gas is C₄F₈, the inert gas is argon, the chamber ismaintained at below about 200 mT, the RF power is about 1800 watts, themagnetic field is about 30 G and the chamber is exhausted at from about1,600 liters per second to about 2,000 liters per second.

[0220]FIGS. 36A and 36B illustrate feature structures representative ofa mask open application. FIGS. 36A and 36B are not drawn to scale. Somemask materials, such as for example, silicon nitride, are considerablymore difficult to etch than other mask materials and are referred to as“hard masks.” FIG. 36A illustrates pre-hard mask etch structure 3600.While hard masked layer 3615 may be formed over a wide variety of otherlayers and materials, FIGS. 36A and 36B illustrate a hard mask layer3615 deposited directly on a silicon substrate 3610 formed from asuitable hard mask material, such as for example, silicon nitride.Nitride hard masks comprise, for example, active area hard mask etchingand deed conductor hard mask etching. FIG. 36A also illustrates the useof an antireflective coating layer 3620 below photomask pattern layer3625. FIG. 36B illustrates post hard mask etch structure 3605 where thepattern of photomask layer 3625 has been transferred into hard masklayer 3615 by a suitable hard mask etch process performed in and etchprocessing chamber having embodiments of the present invention.

[0221] The suitable hard mask open process chemistry comprises a gascomposition comprising a hydrofluorocarbon gas, a fluorocarbon gas andan oxygen comprising gas wherein the total gas flow of the gascomposition is from about 50 sccm to about 200 sccm. In a specificembodiment, the hydrofluorocarbon gas comprises more than about half ofthe total gas composition flow rate and the oxygen comprising gas flowrate comprises less than about 15 percent of the total gas compositionflow rate. In another specific embodiment, the ratio of the flow rate ofthe hydrofluorocarbon gas to the flow rate of the fluorocarbon gas isabout 1.5:1. In another specific embodiment, the ratio of the combinedhydrofluorocarbon gas flow rate and the fluorocarbon gas flow rate tothe flow rate of the oxygen comprising gas is about 5.5:1.

[0222] In a specific preferred embodiment, the hydrofluorocarbon gas isa CHF₃, the fluorocarbon gas is a CF₄, the oxygen comprising gas is O₂,the pressure in the process chamber is maintained from about 20 mT toabout 80 mT and the RF power is about 500 watts. In yet another specificembodiment, the substrate support is maintained about 15 degrees Celsiushigher than a temperature of an adjacent wall, or preferably, atemperature controlled liner.

[0223]FIGS. 37A and 37B illustrate, respectively, pre-etch spacerstructure 3700 and post etch spacer structure 3705. FIGS. 37A and 37Bare not illustrated to scale. Pre-etch spacer structure 3700 illustratesa feature 3715 formed over an underlayer 3720 on top of a siliconsubstrate 3710. A dielectric layer 3725 is formed over both the feature3715 and the underlayer 3720. Post etch spacer structure 3705 of FIG.37B is formed after conducting a suitable spacer etch process asdescribed in greater detail below. In post spacer etch structure 3705,spacer feature 3725 is formed by etching dielectric layer 3725 to exposethe top portion of the feature 3715 and remove most of the underlayer3720. In a representative spacer structure, feature 3715 could be formedfrom polysilicon and the underlayer 3720 could be formed from silicondioxide.

[0224] In general, spacer etch processes may be divided into twocategories based upon selectivity to the underlayer 3720. For example,in the illustrated spacer structure described above, the spacer etchprocess is selective to an underlying silicon dioxide layer.Alternatively, when removal of both dielectric layer 3725 an underlyinglayer 3720 is desired, a spacer etch process selective to the siliconsubstrate 3710 may be used in order to etch both dielectric layer 3725and underlying layer 3720 before stopping upon reaching siliconsubstrate 3710.

[0225] The gas composition used to form a suitable spacer etch processchemistry comprises a hydrofluorocarbon gas, a fluorocarbon gas, anoxygen comprising gas and an inert gas with a total gas flow of the gascomposition is from about 50 sccm to about 200 sccm. In a specificembodiment, the hydrofluorocarbon gas flow comprises more than about 40percent of the total gas flow and the oxygen comprising gas comprisesless than about 5 percent of the total gas composition flow rate. Inanother specific embodiment, the ratio of the hydrofluorocarbon gas flowto the fluorocarbon gas flow is about 2.5:1. In yet another specificembodiment, the combined flow rate of the hydrofluorocarbon gas and thefluorocarbon gas to the flow rate of the inert gas is about 1.75:1.

[0226] In a specific preferred embodiment, the fluorocarbon gas is CF₄,the hydrofluorocarbon gas is CHF₃, the oxygen comprising gas is O₂, theinert gas is argon, the pressure of the etch chamber is maintained atbetween about 20 mT to about 80 mT, the RF power is about 400 watts, thesubstrate support is maintained at a temperature about 25 degreesCelsius higher than an adjacent wall, or preferably, an adjacent directtemperature controlled liner.

[0227]FIGS. 38A and 38B illustrate representative structures for etchingdual damascene features. FIG. 38A illustrates pre-dual damascenedielectric etch structure 3800 and FIG. 38B illustrates post dualdamascene dielectric etch structure 3805. FIGS. 38A and B are notillustrated to scale.

[0228]FIG. 38A illustrates a basic dual damascene structure formed overin metal layer, such as for example, a copper layer 3810. Two dielectriclayers, namely trench dielectric layer 3830 and via dielectric layer3820, are etched during a suitable dual damascene dielectric etchprocess, such as those discussed in more detail below. A bottom nitridelayer 3815 separates the copper layer 3810 from the via dielectric layer3820. Intermediate nitride layer 3825 separates the trench dielectriclayer 3830 from the via dielectric layer 3820. In some dual damasceneetch processes, the intermediate nitride layer 3825 is used as a stoplayer for etching the trench dielectric layer 3830 and the bottomnitride layer 3815 is used as a stop layer for etching the viadielectric layer 3820. FIG. 38B illustrates post dual damascene etchstructure 3805 that includes a via feature 3850 and an interconnectfeature 3855. Typically, the via feature 3850 and the interconnectfeature 3855 are filled by subsequent metalization processes.

[0229] There are at least three fundamental process flows used to formdual damascene features: self aligned, trench first, and via first.While other structures may be and are used, in general, typical dualdamascene etch processes begin with a pre-etch structure, such asstructure 3800 of FIG. 38A, and finish with a structure having a viafeature 3850 and an interconnect feature 3855 as illustrated in FIG.38B.

[0230] In a self aligned dual damascene process, a via pattern is etchedfirst by opening intermediate nitride layer 3825. During a subsequentetch step that uses bottom nitride layer 3815 as an etch stop layer,both the via feature 3850 and the interconnect feature 3855 are formed.Finally, the bottom nitride layer 3815 is removed to expose copper layer3810.

[0231] In a trench first dual damascene process, the mask pattern layer3835 forms the pattern for the interconnect feature 3855 and the upperportion 3860 of the via feature 3850. The resulting intermediatestructure comprises interconnect 3855 and the upper portion of viafeature 3860. This intermediate structure is then patterned and etchedto form the lower portion of via feature 3865 using bottom nitride layerof 3815 as an etch stop layer. A subsequent etch step is then used toremove bottom nitride layer 3815 and expose the copper layer 3810.

[0232] In a via first dual damascene process, a via pattern is formed bythe mask pattern layer 3835. The via pattern is subsequently transferredto both of the dielectric layers 3830 and 3820 and to the intermediatenitride layer 3825. This step forms an intermediate structure comprisingthe lower portion 3865 of via structure 3850. Next, a trench maskpattern is formed over this intermediate structure to pattern thetrenches, namely the interconnect feature 3855 and the upper portion ofcontact feature 3860. The bottom nitride layer 3815 is subsequentlyremoved exposing the copper layer 3810.

[0233] The exact dimensions of the dual damascene structures 3800 and3805 will vary depending upon a number of considerations, such as forexample, the type of dual damascene process sequence and the designrules of a particular device. The particular design rules determine thedimensions for trench feature 3855, via feature 3850 and, moreimportantly, the critical dimension of contact region 3865. Etch processchambers having embodiments of the present invention are capable ofetching dual damascene structures having critical dimensions of about0.3 microns to about 0.25 microns and even structures having criticaldimensions of about 0.1 microns to about 0.2 microns.

[0234] A suitable dual damascene trench etch process chemistry comprisesa fluorocarbon gas having a carbon to fluorine ratio of about 1:3 and agas comprising carbon and oxygen. In a preferred embodiment, most of thegas composition comprises a gas comprising carbon and oxygen with thetotal flow of the gas composition being from between about 200 sccm toabout 400 sccm. In a specific preferred embodiment, at least about 60percent of the gas composition comprises a gas comprising oxygen andcarbon. In another specific embodiment, the ratio of the flow rate ofthe gas comprising oxygen and carbon to the flow rate of thefluorocarbon gas is about 1.67:1. In yet another specific preferredembodiment, the fluorocarbon gas is C₂F₆, the gas comprising oxygen andcarbon is CO, the pressure to processing chamber is maintained atbetween about 100 mT to about 200 mT, the magnetic field in theprocessing region is about 30G and the RF power is about 1500 watts.

[0235] In an alternative embodiment where the dual damascene structurecomprises a nitride stop layer, a suitable dual damascene etch processchemistry comprises a gas composition comprising a polymerizingfluorocarbon having a C:F ratio of about 1:2, and oxygen comprising gasand an inert gas. In a specific preferred embodiment, the inert gascomprises more than about 90 percent of the total gas composition flow,and the oxygen comprising gas comprises less than about 1 percent of thetotal gas composition flow. In another specific preferred embodiment,the ratio of the inert gas flow to the combined flow rates of thepolymerizing fluorocarbon gas and the oxygen comprising gas is fromabout 20:1 to about 22:1. In a specific preferred embodiment thepolymerizing fluorocarbon gas is C₄F₈ and the oxygen comprising gas isO₂ and the ratio of the C₄F₈ flow rate to the O₂ flow rate is about 3:1about 4:1. In a specific preferred embodiment, the gas compositioncomprises a C₄F₈, O₂ and Ar wherein the Ar flow rate is more than about95 percent of the total gas composition flow rate, the C₄F₈ flow ratecomprises more than about three percent of the total gas compositionflow rate, the chamber is maintained at about 80 mT, the RF power levelis about 1800 watts, the magnetic field in a processing region is about20G, the substrate support is maintained at about 10 degrees Celsiushigher than the temperature of an adjacent wall or, preferably, atemperature controlled liner.

[0236] One suitable dual damascene via etch chemistry comprises a gascomposition comprising a fluorocarbon gas having a C:F ratio of about2:3, and oxygen comprising gas and an inert gas. In a specific preferredembodiment, the etch chamber is maintained between about 30 mT to about80 mT, the total gas composition flow rate is from about 300 sccm toabout 500 sccm an and the ratio of the inert gas flow rate to thecombined flow rates of the fluorocarbon gas having a C:F ratio of about2:3 and an oxygen comprising gas is from about 5:1 to about 7:1 and morepreferably, about 6:1. In a specific preferred embodiment, thefluorocarbon gas having a C:F ratio of about 2:3 is C₄F₆, the oxygencomprising gas is O₂ and inert gas is argon, the C₄F₆ comprises about 5%to about 9% of the total gas composition flow and the inert gas flowcomprises more than about 80 percent of the gas composition flow, thechamber is maintained at about 50 mT, the RF power is about 1800 wattsand a magnetic field in the processing region is about 50 G.

[0237] In another alternative embodiment, a two-step dual damascene viaetch process may be used. A suitable to two-step dual damascene via etchprocess chemistry comprises a gas composition comprising a polymerizingfluorocarbon gas, a hydrofluorocarbon gas, an oxygen comprising gas andan inert gas wherein the ratio of the inert gas flow to the combined gasflows of the polymerizing fluorocarbon gas, the hydrofluorocarbon gasand the oxygen comprising gas is from about 4:1 to about 6:1; and thepolymerizing fluorocarbon gas used in the second step is greater thanthe first step. In a specific preferred embodiment of a suitabletwo-step dual damascene via process, the first step gas compositioncomprises less than about three percent polymerizing fluorocarbon gas,about 4 percent to about 5 percent oxygen comprising gas, about 7percent to about nine percent hydrofluorocarbon gas and more than about80 percent inert gas while the second step comprises more than about 4percent polymerizing fluorocarbon gas, about 4 percent to about 5percent oxygen comprising gas, about 7 percent to about 8 percenthydrofluorocarbon gas and more than about 80 percent inert gas. In aspecific preferred embodiment, the total gas composition flow rate ineach etch step is from about 500 sccm to about 1,000 sccm, the pressureis about 50 mT, the RF power level is about 2,000 watts and the magneticfield apply to the processing region is about 15G. In another specificpreferred embodiment, the polymerizing fluorocarbon gas is C₄F₆, thehydrofluorocarbon gas is CHF₃, the oxygen comprising gas is O₂ and theinert gas is Ar.

[0238] It is to be appreciated that each of the alternative etch processchamber embodiments and critical etch processes described above mayincorporate aspects of the high exhaust pump rate and reduced reactivespecies residence time control feature of the present invention.

[0239] The terms “below”, “above”, “bottom”, “top”, “up”, “down”,“first”, and “second” and other positional terms are shown with respectto the embodiments in the figures and may be varied depending on therelative orientation of the processing system.

[0240] Furthermore, in this specification, including particularly theclaims, the use of “comprising” with “a” or “the”, and variationsthereof means that the item(s) or list(s) referenced includes at leastthe enumerated item(s) or list(s) and furthermore may include aplurality of the enumerated item(s) or list(s), unless otherwise stated.

[0241] Although the embodiment of the invention which incorporate theteachings of the present invention which has been shown and described indetail herein, those skilled in the art can readily devise other variedembodiments which still incorporate the teachings and do not depart fromthe spirit of the invention.

What is claimed is:
 1. A method of etching features on a dielectriclayer on a substrate, comprising: (a) disposing a substrate in aprocessing region of a plasma etch chamber; (b) controlling thetemperature of a substrate support; (c) maintaining a low pressure inthe processing region; (d) flowing a gas composition comprisinghexafluoro-1, 3-Butadiene, oxygen and argon, into the processing region;(e) capacitively coupling RF energy into the processing region to form aplasma from the gas composition; and (f) providing a magnetic field inthe processing region.
 2. The method of claim 1, wherein said flowing agas composition is performed at total gas flow from 40 sccm to 1000sccm.
 3. The method of claim 1, wherein said maintaining a low pressurecomprises evacuating the chamber using a vacuum pump system havingcapacity of at least 1600 liter per minute.
 4. The method of claim 1,wherein flow ratio of argon to hexafluoro-1, 3-Butadiene is from about5:1 to about 20:1.
 5. The method of claim 1, wherein said maintaining alow pressure comprises maintaining the chamber pressure from about 20 mTto about 250 mT.
 6. The method of claim 1, wherein said maintaining alow pressure comprises evacuating the chamber using a vacuum pump systemso as to provide a residence time of reactive species in the processingregion of less than about 70 ms.
 7. A method of plasma etching featureson a dielectric layer on a substrate disposed in a capacitively coupledplasma etch chamber, comprising: (a) disposing a substrate in aprocessing region of a capacitively coupled plasma etch chamber; (b)controlling the temperature of a substrate support; (c) maintaining alow pressure in the processing region by evacuating the chamber using avacuum pump system having capacity of at least 1600 liter per minute;(d) flowing a gas composition comprising linear C4F6 oxygen and argon,into the processing region; (e) capacitively coupling RF energy into theprocessing region to form a plasma from the gas composition; and (f)cooling said substrate while it is being etched by said plasma.
 8. Themethod of claim 7, wherein said flowing a gas composition is performedat a total gas flow from 40 sccm to 1000 sccm.
 9. The method of claim 7,wherein flow ratio of argon to linear C4F6 is from about 5:1 to about10:1.
 10. The method of claim 7, wherein said maintaining a low pressurecomprises maintaining the chamber pressure from about 20 mT to about 250mT.
 11. The method of claim 7, wherein said maintaining a low pressurecomprises evacuating the chamber using a vacuum pump system so as toprovide a residence time of reactive species in the processing region ofless than about 70 ms.
 12. A method of etching features on a dielectriclayer on a substrate, comprising: (a) disposing the substrate in aprocessing region of the reactor chamber; (b) flowing a gas compositioncomprising linear C4F6, oxygen and argon into the processing region at ahigh gas composition flow rate and a high argon-to-C4F6 flow ratio; (c)capacitively coupling RF energy into processing region to form a plasmafrom the gas composition; (d) maintaining a low pressure in said chamberby evacuating said gas composition at a high evacuation rate.
 13. Themethod of claim 12 wherein the step of maintaining a low pressure insaid chamber comprises evacuating said chamber with a pump having acapacity of at least about 1600 liters per minute.
 14. The method ofclaim 12 wherein said high evacuation rate is sufficient to maintain aresidence time of species of said gas composition on the order of about70 ms or less.
 15. The method of claim 12 wherein said low pressure isin a range of about 20 mT to 250 mT.
 16. The method of claim 15 whereinsaid high gas composition flow rate is in a range of about 40 sccm to1000 sccm.
 17. The method of claim 16 wherein said high argon-to-C4F6flow ratio is in a range of about 5:1 to 20:1
 18. The method of claim 12further comprising providing a magnetic field in the processing region.19. The method of claim 18 wherein said magnetic field is a rotatingmagnetic field.
 20. The method of claim 19 wherein said magnetic fieldhas a strength in the range of about 100 Gauss to 150 Gauss.
 21. Amethod of etching features on a dielectric layer on a substrate,comprising: (a) disposing the substrate in a processing region of thereactor chamber; (b) cooling said substrate; (c) cooling a wall of saidchamber to a sufficiently low temperature to promote adhesion of polymermaterials on said wall; (d) flowing a gas composition comprising lineara species containing hexafluorobutadiene, oxygen and argon through anoverhead gas distribution apparatus into the processing region at a highgas composition flow rate and a high argon-to-flourocarbon flow ratio;(e) capacitively coupling RF energy into processing region to form aplasma from the gas composition; and (f) maintaining a low pressure insaid chamber by evacuating said gas composition at a high evacuationrate.
 22. The method of claim 21 wherein the step of maintaining a lowpressure in said chamber comprises evacuating said chamber with a pumphaving a capacity of at least about 1600 liters per minute.
 23. Themethod of claim 21 wherein said high evacuation rate is sufficient tomaintain a residence time of species of said gas composition on theorder of about 70 ms or less.
 24. The method of claim 21 wherein saidlow pressure is in a range of about 20 mT to 250 mT.
 25. The method ofclaim 24 wherein said high gas composition flow rate is in a range ofabout 40 sccm to 1000 sccm.
 26. The method of claim 25 wherein said highargon-to-fluorocarbon flow ratio is in a range of about 5:1 to 20:1 27.The method of claim 26 further comprising providing a magnetic field inthe processing region.
 28. The method of claim 27 wherein said magneticfield is rotating magnetic field.
 29. The method of claim 28 whereinsaid magnetic field has a strength in the range of about 100 Gauss to150 Gauss.
 30. The method of claim 21 wherein the step of flowing a gascomposition comprises introducing the gas composition through a gasdistribution apparatus in a ceiling of the chamber overlying thesubstrate.
 31. A method of performing a self-aligned contact etchprocess on a semiconductor substrate with a plasma etch reactor,comprising: (a) disposing the substrate in a processing region of theplasma reactor; (b) flowing a gas composition comprisinghexafluorobutadiene, oxygen and argon (c) capacitively coupling RFenergy into processing region to form a plasma from the gas composition;and (d) maintaining a low pressure in said chamber by evacuating saidgas composition at a high evacuation rate.
 32. The method of claim 31further comprising: cooling a wall of said chamber to a sufficiently lowtemperature to promote adhesion of polymer materials on said wall. 33.The method of claim 31 wherein the step of flowing a gas compositioncomprises introducing the gas composition into the processing regionthrough an overhead gas distribution apparatus.
 34. The method of claim31 wherein the step of flowing a gas composition is carried out at ahigh gas flow rate and a high argon-to-flourocarbon flow ratio.
 35. Themethod of claim 31 wherein the step of maintaining a low pressure insaid chamber comprises evacuating said chamber with a pump having acapacity of at least about 1600 liters per minute.